Frond simple, constricted at the middle; end view angular, or circular, with a lobato-radiate margin, or, rarely, compressed with a process at each extremity.
Frond mostly minute, simple, more or less constricted at the middle, and thus forming two segments, which are often somewhat twisted, generally broader than long, and in many species elongated laterally into a process, so that the constriction on each side is a roundish or angular sinus; in other respects the front view shows the segments quite entire.
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The end view varies in form: in most of the species it is triangular or quadrangular, and the angles are either rounded or elongated into rays; in some it is circular with five or more processes forming marginal rays; in a few species it is compressed and the extremities terminate by a process.
Ehrenberg in his great work has distributed the plants, which I shall here describe, among different genera according to the number of angles or processes seen in an end view. Thus he refers those with three angles to Desmidium, and those with four to Staurastrum, and he formed his genus Pentasterias for the reception of a plant with five rays. But this arrangement appears unnatural; not only because it separates nearly allied forms, but also because the number of rays, as Meneghini remarks, is not constant even in the same species: Professor Bailey says, when describing an American species, " The number of arms is usually three, but I have met with specimens in which one corpuscule had three and the other four arms, others in which both had four, and others again in which both had five arms." I have myself seen fronds of Staurastrum paradoxum and S. dejectum, one segment of which had four and the other only three rays. I have generally found the Pentasterias margaritaceum of Ehrenberg with six rays, although not unfrequently with five, and occasionally with seven rays to each segment. Since we already know that about half the British species vary in the number of their rays, and specimens with three rays conjugate with four-rayed ones, the number of rays is not only altogether useless as a generic character, but it does not distinguish species and scarcely indeed varieties.
Staurastrum contains more species than any other genus in the family. M. de Brébisson enumerates forty in a list which he has sent me, to which several must be added that have been figured by Professor Bailey and others. The species exhibit a great variety of forms, and but little affinity can be traced between many of them: --- as, for instance, between Staurastrum tumidum and S. paradoxum, or between S. dejectum and S. bacillare. Nevertheless, desirable as it would be to separate plants so little allied, it seems better to keep them together for the present than prematurely to attempt their separation.
I should greatly have preferred Kützing's name Phycastrum to Staurastrum; for the latter is applicable only to a limited number of the species. Still, as it had been previously employed by Meneghini
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and Brébisson, the rule established in such cases scarcely permits its exchange for the more appropriate term.
Sporangia of several species have been gathered. They are generally spinous, but differ in other respects.
A little care will distinguish Staurastrum from the other genera in this family, although some of its species appear at first sight to approach forms which belong to them. It differs from Desmidium in never forming a filament; and from Arthrodesmus and Cosmarium by its angular shape, or by having the ends elongated into processes. Some species bear a considerable resemblance to species of Xanthidium, to which genus Ehrenberg refers them; but in Xanthidium the frond, irrespective of the spines, is not angular in the end view, and there is a projection at the centre of each segment in the front view.
* Frond smooth, or rough with minute puncta-like granules; end view with the lobes or angles inflated and mucronate or awned.
†
1. S. dejectum (Bréb.); segments smooth, lunate or elliptic; constricted portion very short; end view with inflated awned lobes.
alpha. Segments externally lunate, awns directed outwards.
Staurastrum dejectum, Bréb., Meneghini, Synop. Desmid. in Linnaea 1840, p. 227. Brébisson, in lit. cum icone.
Staurastrum mucronatum beta, Ralfs, in Annals of Nat. Hist. v. 15. p. 152 (1845). t. 10. f. 5.
beta. Segments elliptic, awns parallel.
gamma. Awns converging.
Staurastrum mucronatum alpha. and gamma , Ralfs, in Annals of Nat. Hist. v. 15. p. 152. t. 10. f. 5; Trans. of Bot. Soc. of Edinburgh, v. 2. p. 139. t. 13. Jenner, Fl. of Tunbridge Wells, p. 192.
Goniocystis (Trigonocystis) mucronata, Hass. Brit. Alg. p. 350 (1845).
Common. Dolgelley and Penzance, J. R. Weston Bogs near Southampton; Sussex; Surrey; and Kent, Mr. Jenner. Kerry, Mr. Andrews. Yate near Bristol, Mr. Broome. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Ambleside, Mr. Sidebotham. Rochdale, Mr. Coates.
Falaise, Brébisson. West Point, New York, Bailey.
Frond smooth, deeply constricted at the middle; segments broader than long, lunate or elliptic, awned, the awns subulate, varying in length and direction. The end view shows three or four mammillate lobes or rays, each terminated by a hair-like mucro or awn.
Sporangia of this plant are more commonly met with than those of any other species in the family except Hyalotheca dissiliens. Since I first detected them at Dolgelley, I have gathered them more or less abundantly every year, both at Dolgelley and at Penzance; they have also been sent me by Mr. Jenner, Mr. Broome, Dr. Dickie and Mr. Thwaites.
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The above description of the process applies, with occasional and slight variations, to the conjugation of the greater number of species in the Desmidieae whose sporangia have been noticed; and I have detailed it at length in this place, not only because this species has afforded more numerous opportunities for tracing the formation of its sporangium, but because it was the first example I had witnessed of the spinous kind, and I devoted more time to its examination than to any other.
Either more than one species has been included under this name, or the sporangia vary much in regard to their spines, which in the Penzance specimens are fewer and appear at first like minute tubercles.
Staurastrum dejetum and a few other species form a distinct group, distinguished by their smooth fronds, the peculiar inflated or mammillate form of their angles, or rather lobes, in the end view, and by their terminal awnlike spines. In some respects they have more resemblance to the two plants placed in Arthrodesmus than to the other species of this genus. Should any change be required, I would rather remove them to Arthrodesmus than unite that genus with Staurastrum.
Staurastrum dejectum is larger than S. cuspidatum, its spines are shorter, and its segments are connected either without a band or by a very short one.
Length of frond 1/833 of an inch; breadth 1/757; breadth at constriction 1/2732; length of awn 1/3937; diameter of sporangium 1/714; length of spine of sporangium from 1/2500 to 1/1250.
Tab. XX. fig. 5. a, b, c. front views of frond; d, e. end views; f, g. conjugated fronds; h, i, k, l, m. different states of sporangia.
2. S. cuspidatum (Bréb.); segments smooth, fusiform, connected by a long narrow band; awns parallel or converging, but straight; end view with inflated awned lobes.
Binatella tricuspidata, Brébisson, Alg. Fal. p. 57. t. 8 (1835).
Staurastrum cuspidatum, Bréb., Meneghini, Synop. Desmid. in Linnaea 1840, p. 226. Brébisson, in lit. cum icone.
Phycastrum cuspidatum, Kützing, Phy. Germ. p. 138 (1845).
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Dolgelley and Penzance, J. R. Rochdale, Mr. Coates. Weston Bogs near Southampton, Mr. Jenner.
Falaise, Brébisson. Germany, Kützing.
Frond usually smaller than that of Staurastrum dejectum; segments smooth, fusiform or truncate on the outer side, separated by a long band-like neck which is present also in the dividing frond between the old and new segments; the subulate awns are elongated and straight, and either parallel to those of the other segment or convergent with them. The end view has three or four mammillate and awned lobes.
Staurastrum cuspidatum may be known from S. dejectum by the elongated band which connects the segments.
The sporangium of this species resembles that of S. dejectum, but has fewer spines.
Length of frond 1/883 of an inch; breadth 1/1000; breadth at constriction 1/3937; diameter of sporangium 1/869.
Tab. XXI. fig. 1. a, b. fronds with endochrome; c. frond dividing; d. transverse view; e. end view.
Tab. XXXIII. fig. 10. sporangium.
3. S. aristiferum --- ; segments smooth, the lobes in front view prolonged into mammillate awned projections which are somewhat constricted at the base; end view with three or four awned lobes.
Dolgelley, J. R.
Frond smooth, about as large as that of Staurastrum cuspidatum; segments not separated by a band; ends usually truncate, but the angles are elongated into mammillate processes, each terminated by a long awn; end view as in the two preceding species.
Staurastrum aristiferum may be a variety of S. cuspidatum, but as it has no isthmus between the segments, and the angles in the front view are elongated, I have described it as distinct.
Length of frond 1/657 of an inch; breadth 1/1064. length of spine 1/1923; breadth at constriction 1/2500.
Tab. XXI. fig. 2. a. front view; b. end view.
4. S. Dickiei --- ; segments smooth, subelliptic, turgid; spines short, curved toward those of the other segment; end view with three slightly inflated mucronate lobes.
Aberdeenshire, Dr. Dickie. Dolgelley, J. R.
Frond smooth, larger than that of Staurastrum dejectum, deeply constricted at the middle; segments twice as broad as long, elliptic, but having the outer margin more convex than the inner one; spines short, curved and converging with those of the other segment. End view with three slightly inflated lobes, which are rounded and mucronate.
This plant was first sent me by Dr. Dickie, who pointed out its resemblance in a front view to Arthrodesmus convergens. It is however smaller, although
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it has an additional angle, and I have not detected any mucous covering. From the three preceding species it differs in its more turgid segments and in the short, curved, converging spines. As the sides are but slightly concave, the end view is less decidedly lobed, the angles also are more rounded and less conspicuously mammillate. Staurastrum Dickiei is more like the S. brevispina, Bréb., but that species has larger segments, which are semiorbicular and very turgid, and its spines are very minute, and detected, at least in the dried specimen, with difficulty. The Scotch specimens have their spines smaller than those of the Welsh ones, and therefore approach still more closely to S. brevispina.
Length of frond 1/855 of an inch; breadth 1/929; length of awn 1/3086; breadth at constriction 1/2500.
Tab. XXI. fig. 3. a. front view; b. end view.
5. S. brevispina (Bréb.); segments smooth, turgid, elliptic, minutely mucronate; end view three-lobed, each lobe terminated by a short mucro.
Henfield, and near Pulborough, Sussex, Mr. Jenner. Penzance, J. R.
Falaise, Brébisson.
Frond larger than that of Staurastrum dejectum; segments elliptic or reniform, very turgid, twice as broad as long, having on each side a very minute spine or mucro which is often difficult to detect. A drawing sent me by M. de Brébisson represents the spines subulate and converging with those of the other segment. In Mr. Jenner's specimens there is a minute papilla rather than mucro at each lobe, and in the front view these papillae are situated more outwardly than the spines are in M. de Brébisson's specimens. The end view is three-lobed; the lobes are inflated and have broadly rounded ends.
Length of frond 1/502 of an inch; breadth 1/510; breadth at constriction 1/2041; length of spine 1/12195.
Tab. XXXIV. fig. 7. a. front view; b. end view; c, d. front and end views from drawings by M. de Brébisson.
†† Frond rough with minute granules.
6. S. lunatum --- ; frond rough with puncta-like granules; segments externally lunate, with an awn at each angle; end view with three inflated awned lobes.
Penzance, J. R.
This species resembles in figure Staurastrum dejectum, but it is larger. Frond deeply constricted at the middle; segments semilunate, the convex margins united, the outer margin rough with minute granules and truncate, each angle tipped by an awn or mucro which is directed obliquely outwards. End view three-lobed, the lobes inflated, obtuse and awned.
Its rough frond distinguishes Staurastrum lunatum from all the preceding species, and the inflated awned lobes of its end view from all the following ones.
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Length of frond 1/856 of an inch; breadth 1/686; breadth at constriction 1/2336; length of spine 1/4098.
Tab. XXXIV. fig. 12. a. front view; b. end view.
** Frond smooth; angles in end view broadly rounded.
7. S. muticum (Bréb.); segments smooth, elliptic, end view showing slightly concave sides and 3-5 rounded angles.
Dolgelley and Penzance, J. R. Ambleside, Mr. Sidebotham.
Falaise, Brébisson. Italy, Meneghini.
The frond, generally smaller than that of Staurastrum orbiculare, is quite smooth and has a mucous covering, which is sometimes distinct, but often it can only be ascertained by the appearance of a clear border round the frond which prevents the contact of other substances; segments elliptic. The end view shows three or four angles, sometimes five, according to Meneghini; the sides are slightly concave and the angles broadly rounded.
Staurastrum muticum differs from S. orbiculare by its elliptic segments and mucous covering.
Length of frond 1/674 of an inch; breadth 1/686; breadth at constriction 1/2500.
Tab. XXI. fig. 4. a, b. front view; c. end view of three-rayed state; d. end view of four-rayed variety.
Tab. XXXIV. fig. 13. Sporangium, from a drawing by M. de Brébisson.
8. S. orbiculare (Ehr.); segments smooth, semiorbicular; end view bluntly triangular.
Staurastum trilobum, Meneghini, Conspect. Alg. Eug. p. 18 (1837).
Staurastrum muticum, Bréb. in Menegh. Synop. Desmid. in Linnaea 1840; in lit. cum icone.
Dolgelley and Penzance, J. R. Sussex; Kent; and Weston Bogs near Southampton, Mr. Jenner. Ben Muich Dhu (alt. 3480 feet), Aberdeenshire, Dr. Dickie. Aberdeenshire and Banffshire, Mr. P. Grant. Ambleside, Westmoreland, Mr. Sidebotham.
Germany, Ehrenberg and Kützing. Falaise, Brébisson. West Point, New York, Bailey.
Frond smooth, deeply constricted at the middle; the segments are generally in close approximation for their entire breadth, hence the frond is suborbicular. The end view is triangular, with sides either straight or slightly concave and rounded angles.
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Staurastrum orbiculare may be recognized by its smooth frond, angles broadly rounded and destitute of processes, and its orbicular form in a front view.
Sporangia, gathered at Dolgelley and Penzance, are orbicular, with subulate spines. The conjugating fronds are smaller than those in the ordinary state.
Length of frond 1/1037 of an inch; breadth 1/1106; breadth at constriction 1/3205; diameter of sporangium 1/960; length of spine 1/1736.
Tab. XXI. fig. 5. a, c, d, h. front view; b, f, i. end view; e. transverse view; g. sporangium.
9. S. tumidum (Bréb.); segments smooth, elliptic or suborbicular; end view bluntly triangular each angle terminated by a nipple-like projection.
Piltdown Common, Sussex, Mr. Jenner. Dolgelley and Penzance, J. R.
Falaise, Brébisson.
Frond large and distinctly visible to the naked eye, smooth, deeply constricted at the middle, having a distinct gelatinous covering, which is often marked with close radiating striae; segments elliptic or suborbicular. The end view is triangular or quadrangular, the sides are convex, the angles rounded, and each terminated by a nipple-like process; some of these projections are visible in the front view. In both views the margin of the frond appears striated. The empty frond is minutely punctate.
Length of frond 1/200 of an inch; breadth 1/250; breadth at constriction 1/450.
Tab. XXI. fig. 6. a. front view; b. end view of triangular form; c. end view of quadrangular variety magnified only 200 times; d. transverse view.
*** Frond with simple spines, hairs, or (rarely) acute granules; angles, in end view, broadly rounded and entire.
Staurastrum orbiculare, Meneghini, Synop. Desmid. in Linnaea 1840, p. 225.
Staurastrum tumidum, Brébisson, in lit. cum icone (1846).
10. S. muricatum (Bréb.); segments semiorbicular, rough with conic granules; end view triangular, with convex sides and broadly rounded angles.
Desmidium apiculosum, Ehrenberg, Infus. p. 142 (1838). Pritchard, Infus. p. 184.
Staurastrum muricatum, Brébisson, Meneghini, Synop. Desmid. in Linnaea 1840, p. 226.
Xanthidium deltoideum, Corda, Observ. Microscopiques sur les Animalcules de Carlsbad, p. 29. t. 5. f. 38, 39 (1840).
Staurastrum muricatum beta, Ralfs, Annals of Nat. Hist. v. 15. p. 154. t. 11. f. 1. d, e. (1845); Trans. of Bot. Soc. of Edinburgh, v. 2. p. 141. t. 14.
Phycastrum apiculosum, Kützing, Phy. Germ. p. 137 (1845).
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Sussex, Mr. Jenner. Dolgelley, J. R.
Falaise, Brébisson. Germany, Ehrenberg, Corda, Kützing.
Frond deeply constricted at the middle, nearly equal in length and breadth, rough with minute conic granules or spines. End view triangular, its sides convex and angles broadly rounded.
Staurastrum muricatum is larger than S. hirsutum, and not hirsute, but rough with stout short granules or spines; in the end view also the sides are more convex.
Length of frond 1/409 of an inch; breadth 1/474.
Tab. XXII. fig. 2. a. front view; b. end view.
11. S. hirsutum (Ehr.); segments semiorbicular, rough with numerous hair-like spines; end view with three rounded angles and straight or slightly convex sides.
Dolgelley and Penzance, J. R. Sussex, Mr. Jenner. Ambleside, Mr. Sidebotham. Rochdale, Mr. Coates. Yate, Mr. Broome. Aberdeenshire, Mr. P. Grant.
Germany, Ehrenberg, Kützing. Falaise, Brébisson.
Frond variable in size, about equal in length and breadth, deeply constricted at the middle; segments semiorbicular, hirsute rather than spinous; hairs numerous, scattered. End view triangular; the sides straight or slightly convex, and the angles broadly rounded.
Sporangia of Staurastrum hirsutum have been gathered abundantly at West Point, New York, by Prof. Bailey. I have gathered sporangia at Dolgelley and Penzance. They are orbicular, their spines short, and branched at the apex.
The hair-like spines are characteristic of this species.
Length of frond from 1/676 to 1/468 of an inch; breadth from 1/833 to 1/680; breadth at constriction 1/2300; diameter of sporangium from 1/744 to 1/480; length of spine of sporangium 1/2040.
Tab. XXII. fig. 3. a. front view of frond with endochrome; b. front view of empty frond; c. end view of frond with endochrome; d. end view of empty frond; e. transverse view; f. immature sporangium; g, h. mature sporangia.
12. S. teliferum --- ; segments reniform, bristly; end view triangular, with concave sides and broadly-rounded bristly angles.
Dolgelley and Penzance, J. R. Ambleside, Mr. Sidebotham. Hadlow Down near Mayfield, and several other stations in Sussex, Mr. Jenner.
Frond about as large as that of Staurastrum hirsutum, deeply constricted at the middle; segments twice as broad as long, somewhat reniform, and furnished with scattered spines. End view triangular; the spines variable in number and confined to the angles.
Staurastrum teliferum differs from S. hirsutum in its longer spines, which are also fewer, stouter, and in the end view confined to the angles. It is a larger plant than S. Hystrix; its spines are more numerous, and the end margins in the front view are convex.
Length of frond 1/597 of an inch; breadth 1/643; breadth at constriction 1/2041; length of spine 1/4098; diameter of sporangium 1/738; length of spine of sporangium 1/2066.
Tab. XXII. fig. 4. a. front view; b. end view.
Tab. XXXIV. fig. 14. Sporangium.
13. S. Hystrix --- ; segments subquadrate, spinous; end view with three or four rounded angles, each furnished with a few subulate spines.
Dolgelley, J. R. Near Storrington, Sussex, Mr. Jenner.
Frond very minute, smaller than that of any other species with simple spines, deeply constricted at the middle; segments spinous, somewhat quadrilateral, about twice as broad as long, the end margin nearly straight. The spines are subulate, few in number, and in the front view most of them are lateral. The end view is triangular or quadrangular, and has concave sides and rounded angles. Six or eight spines are scattered on each angle, the sides and disk being naked.
Its smaller size and differently shaped segments will distinguish this species from Staurastrum teliferum.
Length of frond from 1/1075 to 1/1020 of an inch; breadth from 1/1165 to 1/954; breadth at constriction 1/1165; length of spine 1/6024.
Tab. XXII. fig. 5. a. front view of frond with endochrome; b. front view of empty frond; c. end view; d. transverse view of four-rayed variety.
14. S. quadrangulare (Bréb.); frond smooth; segments quadrangular, with a few marginal spines or teeth; end view quadrilateral, with truncate angles either emarginate or dentate.
Ambleside, Mr. Sidebotham.
Falaise, Brébisson.
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Frond very minute, smooth, deeply constricted at the middle, the constriction forming a linear notch on each side; segments quadrilateral, twice as broad as long, with one or two minute but stout teeth at each angle. End view quadrangular, the sides concave, the angles truncate, and in British specimens emarginate.
A drawing of Staurastrum quadrangulare sent me by Brébisson represents a much larger form. Its angles, which in the end view are broader, have four teeth at their truncate ends and two minute teeth on their upper surface; but I concur with Mr. Jenner in regarding the British plant as a small variety of this species.
Length of frond 1/1157 of an inch; breadth 1/1163; breadth at constriction 1/2193.
Tab. XXII. fig. 7. a. front view with endochrome; b. empty frond; c. end view.
Tab. XXXIV. fig. 11. a. front view from a drawing by M. de Brébisson; b. end view.
15. S. sexcostatum (Bréb.); segments in the front view with a toothed angle at each side; end view circular, with five or six broad, short, toothed lobes.
Very rare. Between Mayfield and Hadlow Down, Sussex, Mr. Jenner. Yate near Bristol, Mr. Thwaites. Dolgelley, J. R.
Falaise, Brébisson.
Frond large, rough with conic granules which give a dentate appearance to the outline; segments about as broad as long, produced into a toothed angle on each side, where also a triangular sinus is formed between the angles. The end view is circular and elevated in the centre, and has five or six broad, short, toothed, marginal lobes. The transverse view has a large central opening surrounded by a row of large granules.
I refer this plant to Brébisson's Staurastrum sexcostatum, on his own authority, but a drawing sent by him of S. sexcostatum represents a smaller state.
Length of frond 1/661 of an inch; breadth from 1/833 to 1/694; breadth at constriction 1/1597.
Tab. XXIII. fig. 5. a. front view of Sussex specimen; b, c. end views; d. transverse view; e. front view of Dolgelley specimen.
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***** Frond smooth; end view acutely triangular, with two accessory subulate spines to each angle.
16. S. monticulosum (Bréb.); segments with a forked spine on each side, and at the end about four short, stout, acute projections; end view acutely triangular, with a bifid appendage to each angle.
Penzance; very rare, J. R.
Falaise, Brébisson.
Frond smooth, rather large, deeply constricted at the middle; segments a somewhat elliptic, with a projection on each side forked like the tail of a swallow. The end margin has generally four remarkable projections, which are stout, twice as long as broad, acute, and look not unlike a cluster of pyramids. The end view is triangular, the angles acute. At the base of each angle, on the upper surface, is a bifid projection, the acute points of which appear on each side.
Stauratrum monticulosum is a remarkable species, difficult to describe, but easily recognized by its figure *.
Tab. XXXIV. fig. 9. a. front view of French specimen; b. end view; both from drawings by M. de Brébisson.
17. S. pungens (Bréb.); frond smooth, each end with about six subulate spines, directed outwards; each angle in the end view tapering into a spine, which has two smaller ones at its base.
Penzance; rare, J. R. Cross-in-Hand, Sussex, Mr. Jenner.
Falaise, Brébisson. West Point, New York, Bailey.
Frond smooth, deeply constricted at the middle; segments externally lunate, and having on the outer margin about six subulate spines, the lateral ones being the most conspicuous. The end view has three angles which taper gradually into subulate spines; its upper surface has two smaller spines at the base of each angle, which diverge and become visible on opposite sides.
Staurastrum pungens agrees with S. monticulosum in having two spines on the upper surface of each angle; but its spines are more slender, and in the front view are all simple and directed outwards.
Tab. XXXIV. fig. 10. a. front view; b, c. end views.
* "S. monticulosum, Bréb., cellulis e dorso triangularibus, apicibus acutissimis, suprapositione bifidis, prominentia bifido-divaricata breviore, quoque angulo superimposita, prominentiis in centro confluentibus, a latere ellipticis utrinque bifidis, exterius dentatis." --- Meneghini.
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****** Frond smooth; front view with diverging processes divided at the apex.
18. S. brachiatum --- ; frond smooth; front view with thick diverging processes which are deeply bifid or trifid at the apex; end view with three or four rays.
Dolgelley and Penzance, J. R. Near Bristol, Mr. Broome. Ambleside, Mr. Sidebotham. Craigendurroch and Glen Lin, Aberdeenshire, Dr. Dickie. Aberdeen, Mr. P. Grant. Reigate, Mr. Jenner.
Frond minute, smooth, scarcely constricted at the middle, truncate at the ends; segments with three or four elongated, straight, tapering processes, which are directed outwards, and consequently diverge from those of the other segment. In the front view each segment usually exhibits only two processes, the others being hidden behind them. The processes are usually trifid at the extremity, though sometimes merely bifid, in which latter case their diverging points are forked like the tail of a swallow: the same bifid appearance may occur in certain positions, even when three points are present. The end view has three or four rays, hyaline, stout at their base, and gradually tapering. In this view, as the frond is generally twisted, the rays of the lower segment may be faintly seen between those of the nearer one.
Sporangia have been gathered by Mr. Broome at Yate near Bristol; they are quadrate and spinous, and afford the only known example of a quadrate sporangium bearing spines. The emptied segments are easily detached; the spines are subulate and few.
Staurastrum brachiatum may always be distinguished from S. paradoxum and S. tetracerum by its smooth and divided processes.
Length of frond 1/1111 of an inch; breadth 1/1785; length of process from 1/1633 to 1/1165; length of sporangium from 1/1020 to 1/868; length of spine from 1/2732 to 1/2048.
Tab. XXIII. fig. 9. a. front view of frond; b, c. dividing fronds; d. end view of four-rayed variety; e, f , g. sporangia.
19. S. laeve --- ; frond smooth; segments with short processes forked at the apex and directed outwards; end view with three or four bipartite angles.
Pool near the outlet of Llyn Gwernan, Dolgelley, J. R.
Fronds very minute, smooth, deeply constricted at the middle, the constriction producing a wide triangular notch on each side. Segments externally lunate or somewhat cuneate, but in general the outer margin is slightly protuberant at the middle. Each angle terminated by a pair of short, stout, hyaline
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processes, which are slightly forked at the apex and directed outwards; but in the front view seldom more than three or four processes are seen at once. End view with three or four bipartite angles, their divisions divergent, subulate, generally appearing acute at the apex, but sometimes, especially if looked at obliquely, forked as in the front view.
Staurastrum laeve, in the front view, agrees with S. brachiatum in its smooth frond and forked divergent processes; but the constriction at the middle is greater, the processes are shorter, and if an angle be towards the eye its geminate character will be detected without much difficulty. In the end view this species is unlike any other.
Length of frond 1/1220 of an inch; breadth 1/2127; breadth at constriction 1/2500; length of process from 1/3546 to 1/3268.
Tab. XXIII. fig. 10. a, b, c. front views; d. end view; e. transverse view.
******* Frond rough with puncta-like granules.
20. S. alternans (Bréb.); segments rough, narrow-oblong, and, from their twisted position, unequal in the front view; end view with the angles of one segment entire, and alternating with those of the other.
Dolgelley and Penzance, J. R. Barmouth, Rev. T. Salwey. Weston Bogs near Southampton; and several stations in Sussex, Surrey and Kent, Mr. Jenner. Near Bristol, Mr. Thwaites. Glen Lin, Aberdeenshire (alt. 1300 feet), Dr. Dickie. Near Aberdeen, Mr. P. Grant. Ambleside, Mr. Sidebotham.
Falaise, Brébisson. West Point, New York, Bailey.
Frond rough with minute pearly granules, which, except on the margin, appear like puncta; segments two or three times longer than broad, oblong, twisted, so that in the front view one of them appears shorter on one side, in consequence of the blending together of two of the angles. The end view is triangular, with concave sides and very obtuse entire angles. The angles of the lower segment are seen alternating with those of the upper.
I formerly described this plant as the Staurastrum tricorne, but that species in the front view is prolonged at the sides into short processes; I am not certain that the two are distinct, but in doubtful points I think it right to defer to M. de Brébisson's opinion.
Staurastrum alternans may be known from S. dilatatum and S. punctulatum by its unequal segments in the front view and alternating angles in the end one.
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I have gathered the sporangia at Penzance; they are orbicular and furnished with spines forked at the apex.
Length of frond 1/1037 of an inch; breadth 1/1106; breadth at constriction 1/3205.
Tab. XXI. fig. 7. a. front view; b. end view; c. transverse view.
21. S. punctulalum (Bréb.); segments rough with puncta-like granules, elliptic, equal; end view with broadly rounded angles and slightly concave sides.
Sussex, Mr. Jenner. Dolgelley, J. R.
Falaise, Brébisson.
Frond larger than that of Staurastrum alternans, rough with minute pearly granules which appear like puncta; segments twice as broad as long, elliptic; end view triangular with very blunt angles.
Staurastrum punctulatum may be distinguished from S. alternans by its equal and more turgid segments in the front view, and in an end one by its less concave sides. S. rugulosum agrees with it in size and partly in form, but in that species the pearly granules are larger and fewer, and at the angles appear like little spines.
Length of frond 1/704 of an inch; breadth 1/881; breadth at constriction 1/2270.
Tab. XXII. fig. 1. a. front view; b. end view of empty frond; c. dividing fronds.
22. S. dilatatum (Ehr.); Segments rough, fusiform, equal; end view with four short, broad, truncate and entire rays.
Dolgelley and Penzance, J. R. Rusthall Common near Tunbridge Wells, and Rackham near Pulborough, Sussex, Mr. Jenner. Yate near Bristol, Mr. Broome. Ambleside, Mr. Sidebotham.
Germany, Ehrenberg, Kützing. Falaise, Brébisson. West Point, New York, Bailey.
Frond very minute, rough with puncta-like pearly granules, deeply constricted at the middle, the sinuses rounded; segments fusiform, two or three times broader than long, equal, obtuse at the sides, and not elongated into processes. In the end view, which is quadrangular, the sides are concave, and the angles form short, broad, truncate rays, on which the granules are arranged
Phycastrum dilatatum, Kützing, Phyc. Germ. p. 138 (1845).
Goniocystis (Staurastrum) dilatatum, Hassall, Brit. Freshwater Algae, p. 353 (1845).
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in transverse lines. Meneghini describes the rays as varying in number from three to five.
Staurastrum dilatatum differs from S. alternans in not being twisted; its rays also (in an end view) are more truncate.
Length of frond 1/1201 of an inch; breadth 1/1381; breadth at constriction 1/3731.
Tab. XXI. fig. 8. a. front view of frond; b. end view; c. transverse view.
23. S. margaritaceum (Ehr.); segments rough tapering at the constriction, and having short lateral processes; end view with five or more short, narrow, obtuse rays.
Pentasterias margaritacea, Ehr. Infus. p. 144. t. 10. f. 15 (1838). Pritch. Infus. p. 185. f. 104.
Staurastrum margaritaceum, Menegh. Synop. Desmid. in Linnaea 1840, p. 227. Ralfs, Annals of Nat. Hist. v. 15. p. 157. t. 11. f. 7; Trans. of Bot. Soc of Edinburgh, v. 2. p. 144. t. 14.
Phycastrum margaritaceum, Kützing, Phycologia Germ. p. 138 (1845).
Goniocystis (Pentasterias) margaritacea, Hassall, Brit. Freshwater Algae, p. 356 (1845).
Dolgelley, J. R. Ashdown Forest, Sussex, Mr. Jenner. Stoke-Hill near Wells, Mr. Thwaites. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Ambleside, Mr. Sidebotham.
Germany, Ehrenberg. Falaise, Brébisson. West Point, New York, Bailey.
Frond rough with minute pearly granules; in the front view the segments are convex at the ends and slightly attenuated at their junction, and on each side there is a short, linear, obtuse and entire process, which is generally somewhat incurved; occasionally these processes are mere conical projections, but they may always be perceived. The end view has from five to seven short, narrow, obtuse, marginal rays.
M. de Brébisson unites S. margaritaceum to S. dilatatum, but they appear to me to be distinct. In the front view of the latter the segments do not taper at their junction, are broader than long, and have no processes visible at the sides; in all which respects it differs from S. margaritaceum.
Length of frond 1/1176 of an inch; breadth, including processes, 1/1000; breadth, excluding processes, 1/2358; breadth at constriction 1/3378.
Tab. XXI. fig. 9. a, b. front views; c, d, e. end views.
24. S. tricorne (Bréb.); frond rough with puncta-like granules; segments tapering at each side into a short, blunt, mostly entire process; end view with three or four blunt angles.
Binatella tricornis, Brébisson, Alg. Fal. p. 57. t. 8 (1835).
Desmidium hexaceros, Ehr. Infus. p. 141. t. 10. f. 10 (1838).
Staurastrum tricorne, Meneghini, Synop. Desmid. in Linnaea 1840, p. 225. Brébisson, in lit. cum icone.
135
Phycastrum tricorne, Kützing, Phycologia Germanica, p. 137 (1845).
Dolgelley and Penzance, J. R., Ambleside, Mr. Sidebotham. Cross-in-Hand, Sussex, Mr. Jenner.
beta. Penzance, J. R. Near Pulborough, Sussex, Mr. Jenner.
Falaise, Brébisson. Germany, Ehrenberg, Kützing.
Frond about as large as that of Staurastrum alternans, deeply constricted at the middle; segments in the front view somewhat fusiform; in an end one showing three or four blunt, generally entire angles.
The segments are frequently more or less twisted, in which case this plant bears a close resemblance to Staurastrum alternans; but I retain the species in deference to the authority of M. de Brébisson; the tapering of the segments at their sides is however its chief distinction.
The sporangia, which I have gathered at Penzance, are orbicular, and furnished with spines divided at the apex.
Length of frond 1/1275 of an inch; breadth 1/948; breadth at constriction 1/3731; diameter of sporangium 1/680; length of spines 1/1457.
beta. Length of frond from 1/1000 to 1/972; breadth from 1/796 to 1/697; breadth at constriction 1/3267; diameter of sporangium 1/909; length of spines 1/1633.
Tab. XXII. fig. 11. a, b. front views of frond; c. end view.
Tab. XXXIV. fig. 8. a. sporangium; b. front view of var. beta ; c. end view; d. sporangium.
†† Angles terminated by minute spines or tapering into slender processes *.
25. S. polymorphum (Bréb.); segments rough with minute granules, having on each side a short process tipped with spines; end view three- to six-rayed.
Dolgelley, J. R. Reigate, Surrey; and near Pulborough, Sussex, Mr. Jenner.
Falaise, Brébisson.
Frond much smaller than that of Staurastrum gracile, deeply constricted at the middle; segments irregular in form, but generally broader than long. Each side terminates in a short truncate projection or process, which is scarcely longer than broad, and tipped by three or four distinct, diverging spines; frequently there are also a few inconspicuous scattered spines on the segment itself. The number of the angles or rays in an end view varies from three to six, but the four-rayed form is the most abundant. The size of the frond is proportionate to the number of these rays.
The sporangia, which I have gathered at Dolgelley, are orbicular; their spines are few and forked at the apex. I have seen three-rayed fronds coupled with four-rayed ones.
* A variety of Staurastrum tricorne has the angles tipped by minute spines, and occasionally Staurastrum cyrtocerum is destitute of spines, excepting those terminating the processes; both forms would therefore be referred to this section.
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The segments are very variable in form and often resemble those of Staurastrum tricorne and S. margaritaceum, but in these species the processes are never spinous. S. polymorphum is smaller and less spinous than S. asperum.
Length of frond 1/1000 of an inch; breadth 1/1157; breadth at constriction 1/2500; diameter of sporangium 1/1000; length of spine of sporangium 1/1106.
Tab. XXII. fig. 9. a, b, c, d. front views; e, f , g. dividing fronds; h. end view of three-rayed segment; i. transverse view of four-rayed segment; k. end view with endochrome; l. end view of empty frond.
Tab. XXXIV. fig. 6. a. front view of variety; b. end view.
26. S. gracile (Ralfs); segments rough, elongated on each side into a slender process which is terminated by minute spines; end view triradiate.
Dolgelley and Penzance, J. R. Ambleside, Mr. Sidebotham. Aberdeen, Mr. P. Grant. Manchester, Mr. Williamson.
New York and New England, Bailey. Falaise, Brébisson.
Frond rough with minute granules, deeply constricted at the middle; segments two or three times longer than broad and tapering, on each side, into a slender, straight and colourless process, which is apparently terminated by three minute points: Mr. Jenner however informs me that the processes really terminate in four points, which are visible only when a process presents its extremity to the observer. The granules are arranged in transverse lines on the processes, and are here more conspicuous than they are on the segment. The end view is triradiate; the colouring matter is restricted to the centre and forms three rays, which are frequently bifid.
Staurastrum gracile differs from S. tricorne in its elongated processes terminated by minute points. The end view somewhat resembles that of S. paradoxum, but the latter species is easily known by the divergent processes of its front view and its smaller size.
Length of frond from 1/773 to 1/539 of an inch; breadth from 1/348 to 1/272; breadth at constriction 1/3105.
Tab. XXII. fig. 12. a. front view; b, c. end views; d. transverse view.
27. S. Arachne (Ralfs); segments rough with minute granules, suborbicular, with elongated, slender, incurved processes; end view with five linear rays.
Staurastrum Arachne, Ralfs, Annals of Nat. Hist. v. 15. p. 157. t. 11. f. 6 (1845); Trans. of Bot. Soc. of Edinburgh v.2. p. 143. t. 14.
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Goniocystis (Pentasterias) arachnis, Hassall, Brit. Freshwater Alg. p. 355 (1845).
Dolgelley, very rare, J. R. Aberdeen, Mr. P. Grant
Falaise, Brébisson.
Frond minute, deeply constricted at the middle; segments about as long as broad, having on each side an elongated process, which is hyaline and incurved, and on account of' its minute granules appears transversely striated. When the frond is viewed obliquely, so that three or more of the long curved processes are seen at once, its resemblance to an insect is considerable. The end view is circular with five slender rays.
This plant is remarkable for its slender processes, which will easily distinguish it from Staurastrum margaritaceum. It cannot be a five-rayed variety of S. gracile or S. polymorphum, for its rays are longer, more slender, remarkably incurved and also entire at the extremity.
Length of frond 1/1020 of an inch; breadth, excluding processes, 1/2040; including processes, 1/652; length of process 1/1858; breadth at constriction 1/2732.
Tab. XXIII. fig. 6. a. front view; b. end view.
28. S. tetracerum (Kützing); frond rough; front view with four slender diverging processes which are entire at the apex; end view compressed, with a process at each extremity.
Dolgelley and Penzance, J. R. Yate near Bristol, Mr. Broome. Aberdeenshire, Mr. P. Grant. Ambleside, Mr. Sidebotham. Midhurst, Battle, and Cross-in-Hand, Sussex, Mr. Jenner.
Germany, Kützing, Ehrenberg. Falaise, Brébisson. United States, Bailey.
Frond very minute; front view nearly square, the angles elongated into straight, slender processes which diverge from each other; frequently however a segment may be so twisted, that one of its processes is situated behind its companion, and is not seen unless carefully looked for; in this case the frond seems to have only three processes in a front view. The end view is much compressed and terminated both ways by an elongated process. The frond is rough with minute puncta-like granules, which form transverse lines on the processes and give them a jointed appearance. The colouring matter is very pale.
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Ehrenberg and Meneghini unite the Micrasterias tetracera of Kützing to the Staurastrum paradoxum, Meyen; but whilst the latter plant has four processes at each end, this has only two, which, if I am correct in my view of the following species, differ also by having entire extremities.
Length of frond 1/2703 of an inch; length of process 1/3030; breadth of frond 1/1785.
Tab. XXIII. fig. 7. a, b, c. front views; d. empty frond; e. frond with one segment not fully developed; f. end view.
29. S. paradoxum (Meyen); frond rough; front view with elongated diverging processes which are minutely trifid at the apex; end view quadrangular or sometimes triangular.
Staurastrum paradoxum, Meyen, Nov. Act. Leop. Holm. v. 14. p. 43. f. 37, 38 (1828). Meneghini, Synop. Desmid. in Linnaea 1840, p. 227. Ralfs, Annals of Nat. Hist. v. 15. p. 151. t. 10. f. 2; Trans. of Bot. Soc. of Edinburgh, v. 2. p. 137. t. 13.
Micrasterias Staurastrum, Kützing, Synop. Diatom. in Linnaea 1833, p. 599.
Phycastrum paradoxum, Kützing, Phycologia Germanica, p. 138 (1845).
Goniocystis (Staurastrum) paradoxum, Hassall, Brit. Freshwater Alg. p. 354 (1845).
Dolgelley and Penzance, J. R. Near Bristol, Mr. Thwaites and Mr. Broome. Ambleside, Mr. Sidebotham. Banffshire and Aberdeenshire, Mr. P. Grant. Near Pulborough, Cross-in-Hand, &c., Sussex, Mr. Jenner.
Germany, Meyen, Kützing. Falaise, Brébisson. West Point, New York, Bailey.
Frond very minute, generally much constricted at the middle, the ends truncate; each segment has, generally, four elongated processes diverging from those of the other segment. The end view is sometimes triradiate, but usually quadriradiate; I have also seen specimens in which one segment had four and the other only three rays. In the front view, as the frond generally rests on one side, each segment appears to have only two processes, the other two being covered by them; but sometimes only one process is thus hidden, and occasionally all four may be seen at the same time. The processes are elongated, colourless, and, being rough with minute granules arranged in transverse lines, have a jointed appearance; each terminates in three minute spines. In the newly-formed segment the processes are mere conical projections.
When only two processes are seen at each end, in the front view, this species is very like the preceding; but its frond is more constricted, larger and of a deeper green, and its processes are thicker and not entire at the apex.
Length of frond 1/941 of an inch; breadth 1/1165; breadth at constriction 1/2923; length of process from 1/1362 to 1/1256.
Tab. XXIII. fig. 8. a, b, c. front views of mature fronds; d, e. end views; f. immature frond.
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******** Frond spinous or rough with spine-like granules which are incrassated, emarginate, or divided *
†
Spines minute, inconspicuous and granule-like.
30. S. cyrtocerum (Bréb.); frond rough with minute granules; segments in the front view somewhat triangular with short incurved processes.
Dolgelley and Penzance, J. R. Near Bristol; Mr. Broome. Piltdown Common and near Pulborough, Sussex, Mr. Jenner.
United States, Bailey. Falaise, Brébisson.
Frond rather larger than that of Staurastrum tricorne, deeply constricted at the middle, rough with minute spine-like granules, which on the processes are arranged in transverse lines. The segments are truncate and taper towards their junction, so that the constriction forms a broad notch on each side. The spines on the outer margin are larger than those on the rest of the segment, and frequently are obscurely notched. The end view has three blunt angles, much like those of Staurastrum tricorne, and usually a little curved.
The sporangia are orbicular and their spines slightly forked at the apex.
Staurastrum cyrtocerum is smaller than S. aculeatum and S. controversum, and its spines are far less conspicuous. It is best distinguished by its converging processes.
Length of frond 1/800 of an inch; breadth 1/500; breadth at constriction 1/2747.
Tab. XXII. fig. 10. a. front view; b. end view.
31. S. asperum (Bréb.); segments elliptic or somewhat cuneiform, rough with minute spines, which on the outer margin are usually dilated at the end or forked.
alpha. Angles in end view rounded.
beta. proboscideum, Bréb.; angles in end view prolonged into short rays terminated by minute spines.
Staurastrum asperum, Brébisson, in lit. cum icone ( 1846).
Penzance, J. R. Yate near Bristol, Mr. Broome and Mr. Thwaites. Near Pulborough, Sussex, Mr. Jenner.
Falaise, Brébisson.<
Frond comparatively large, rough with minute acute granules or spines; segments slightly tapering on the inner side, so that their figure is somewhat cuneate, and the constriction forms a wide notch on each side. The outer
Staurastrum cyrtocerum, Brébisson, in lit. cum icone (1846).
* Staurastrum polymorphum has occasionally a few scattered spines, but they are simple.
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margin is flattened, and its spines are usually more evident than the rest, and are also in general slightly forked. In alpha. the lateral margins are broadly rounded, but in beta. they extend into a process about as long as broad and tipped with a few acute spines, which are larger than those on the segment itself. The end view, in which the sides are nearly straight, has the angles in alpha. rounded, but in beta. terminated by short rays.
The sporangia, which I have gathered at Penzance, are orbicular, and their spines are twice branched at the apex.
The form of the segments distinguishes Staurastrum asperum from all states of S. muricatum. S. punctulatum is smaller, and its granules are more like puncta than spines. In S. rugulosum the segments in the front view are elliptic, not tapering at the junction, and its spine-like granules are confined to the angles.
Length of frond 1/555 of an inch; breadth 1/615; breadth at constriction 1/2403; diameter of sporangium 1/519; length of spines 1/2040.
Tab. XXII. fig. 6. a. front view; b. end view.
Tab. XXIII. fig. 12. a. sporangium; b. front view of variety beta
; c. end view.
††
32. S. Avicula (Bréb.); segments with a forked spine on each side; each angle, in end view, terminated by a mucro-like spine.
Penzance, very rare, J. R.
Falaise, Brébisson.
Frond very minute, scarcely rough, the constriction producing wide triangular notches; segments having on each side a spine forked like the tail of a swallow. End view with three slightly inflated angles or lobes, which are tipped by a spine.
The forked lateral spines of the front view mark the species.
Length of frond 1/907 of an inch; breadth 1/948; breadth at constriction 1/2403; length of spine 1/4098.
Tab. XXIII. fig. 11. a. front view; b. end view.
†††
33. S. enorme --- ; frond irregular or quadrate, spinous; end view three- or four-lobed; lobes broad, more or less emarginate or bifid, and terminated by spines which are either simple or branched.
Dolgelley, J. R.
Frond very irregular and variable in form. Sometimes the front view differs but little from the end one, usually however there is a slight constriction or sinus at the junction of the segments, but I have never observed
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any difference in the endochrome at that part. The spines, which are almost confined to the angles, are irregular, some simple and some branched. The end view has three or four broad and very irregular lobes; these are spinous and more or less emarginate, and frequently one lobe is much broader and more spinous than the others. The spines on each lobe form two groups separated by the notch; they vary much in size, and are either simple and subulate or else forked; sometimes the forked spines are again divided at the apex.
Staurastrum enorme is by far the least symmetrical plant in this family, especially in its front view, and it is very difficult to trace any division into segments. In the end view the broadly emarginate lobes, which, exclusive of the spines, are truncate, afford a good specific distinction between it and any other species.
Length of frond 1/601 of an inch; breadth of lobe in the end view 1/1497.
Tab. XXXIII. fig. 11. a, b, c. front views; d, e. end views.
†††† Spines numerous, conspicuous; angles in end view either rounded, acute, or extended into processes.
34. S. spongiosum (Bréb.); segments semiorbicular, spinulose; spines forked; end view triangular, bordered with forked spines; angles rounded.
Penzance and Dolgelley, rare, J. R. Ashdown Forest, Sussex, Mr. Jenner.
Falaise, Brébisson. West Point, New York, Bailey.
Frond large, about the size of that of Staurastrum muricatum, thickly covered with short spines, which are forked at the apex; segments semiorbicular, having on each side one spine more conspicuous and more forked than the rest. End view triangular, fringed with short notched spines; the sides are slightly convex and the angles rounded.
Staurastrum spongiosum is a very distinct species. In the front view it has some resemblance to Xanthidium armatum, but is much smaller.
Length of frond from 1/506 to 1/418 of an inch; breadth from 1/523 to 1/476; breadth at constriction from 1/833 to 1/738.
Tab. XXIII. fig. 4. a, b. front views; c. end view.
35. S. controversum (Bréb.); frond spinulose; segments with a short process on each side terminated by minute spines; end view with three or four distorted rays.
Staurastrum controversum, Brébisson, Meneghini, Synop. Desmid. in Linnaea 1840, p. 228. Bréb. in lit. cum icone.
Staurastrum aculeatum, Ralfs, Annals of Nat. Hist. v. 15. p. 156. t. 11. f. 4 (1845); Trans. of Bot. Soc. of Edinburgh, v. 2. p. 142. t. 14. Jenner, Fl. of Tunbridge Wells, p. 194.
Goniocystis (Trigonocystis ?) aculeata, Hassall, Br. Freshwater Alg. p. 353 (1845).
Dolgelley and Penzance, J. R. Reigate and Woking Common, Surrey; Cross-in-Hand, Piltdown Common, &c., Sussex, Mr. Jenner, Yate near Bristol, Mr. Broome. Ambleside, Mr. Sidebotham. Aberdeen, Mr. P. Grant.
Falaise, Brébisson.
Frond deeply constricted at the middle; segments broader than long, elliptic or fusiform, often irregular, but usually turgid on the inner side, laterally tapering into a short process, which is terminated by minute spines and generally curved or distorted. The end view is triangular or quadrangular, the angles terminating in short, truncate, curved processes, which, as in the front view, are tipped by minute subulate spines. In both views the fronds show numerous conspicuous spines which are either subulate or notched at the end.
I formerly considered this plant to be the Staurastrum aculeatum, and I still doubt whether it may not be a variety of that species, which scarcely differs except in its processes, which are always straight.
Length of frond 1/972 of an inch; breadth from 1/886 to 1/709. breadth at constriction 1/3731.
Tab. XXIII. fig. 3. a, b, c. front views; d. end view of three-rayed form; e. transverse view; f. view of four-rayed variety; g. transverse view; h. sporangium from a drawing by Brébisson.
36. S. aculeatum (Ehr.); frond spinulose; segments with a short process on each side terminated by minute spines; end view with three to five straight rays terminated by spines.
Desmidium aculeatum, Ehrenberg, Infus. p. 143. t. 10. f. 12 (1838). Pritchard, Infus. p. 184.
Staurastrum aculeatum, Meneghini, Synop. Desmid. in Linnaea 1840, p. 226.
Phycastrum aculeatum, Kützing, Phycologia Germanica, p. 138 (1845).
Weston Bogs near Southampton; and near Pulborough, Sussex, Mr. Jenner. Dolgelley, J. R. Ambleside, Mr. Sidebotham.
Germany, Ehrenberg. Falaise, Brébisson.
Frond about as large as that of Staurastrum controversum, deeply constricted at the middle, the constriction producing a broad triangular notch on each side; segments broader than long, somewhat fusiform, thickly spinulose, the spines simple or notched at the apex. The segments taper on each side into a short process tipped by three or four spines. The end view has from three to five short straight rays terminated by spines.
Length of frond 1/666 of an inch; breadth 1/500; breadth at constriction 1/1666.
Tab. XXIII. fig. 2. a. front view; b. end view of three-rayed form; c. end view of four-rayed variety.
37. S. spinosum (Bréb.); segments elliptic, furnished with a few bifid spines; lateral spines solitary, larger and more forked; end view triangular with two or three spines on each side and one terminating each angle.
Staurastrum spinosum, Brébisson, in lit. cum icone (1847).
Dolgelley and Penzance, J. R. Ambleside, Mr. Sidebotham. Reigate, Surrey, Mr. Jenner.
Falaise, Brébisson.
Frond deeply constricted at the middle; segments subelliptic, their outer margin usually more turgid than the inner; on each side is a conspicuous sessile spine, forked like the tail of a swallow, and on the outer margin are a few smaller spines, which are usually forked at the end, though sometimes simple. End view triangular, each angle terminated by a spine, which appears simple or forked according to its position when viewed; sides with two or three spines, which are sometimes simple and sometimes forked, and on the upper surface are six other spines, one opposite to each lateral spine.
The sporangia of Staurastrum spinosum were first gathered by Mr. Broome near Bristol, and I have since found a few of them at Dolgelley. They are orbicular, and have numerous elongated spines which are divided at the apex.
M. de Brébisson considers this plant identical with the Xanthidium furcatum, Ehr.
Length of frond 1/856 of an inch; breadth 1/907; breadth at constriction 1/3267; diameter of sporangium 1/641; length of spine of sporangium 1/1408.
Tab. XXII. fig. 8. a. front view of frond; b. end view; c, d. sporangia.
38. S. vestitum --- ; frond rough with minute emarginate spines; segments fusiform; end view triradiate, each side having two spines, short, slender, and often accompanied by other smaller ones.
Dolgelley, J. R. Near Pulborough, Sussex, Mr. Jenner.
Frond broader than long, about as large as that of Staurastrum gracile, deeply constricted at the middle, the constriction forming a triangular notch on each side; segments somewhat fusiform, turgid on the inner margin, tapering at each side into a short process which is tipped by three or four minute spines; outer margin fringed with minute emarginate spines or tubercles. End view triradiate, showing also two slender forked spines at the middle of each side, whilst the margin is often fringed with other spines, which are smaller and either simple or notched. The rays are elongate, rough with minute granules, and terminated by minute subulate spines.
In the end view Staurastrum vestitum resembles S. gracile in figure, but that species is not spinous. The rays in the end view are more slender than those of S. aculeatum or S. controversum: but the most distinctive character of this species is the presence of a pair of slender forked spines at the middle of each margin.
Length of frond 1/625 of an inch; breadth 1/384; breadth at constriction 1/3205.
Tab. XXIII. fig. 1. a. front view; b, c. end views with endochrome; d. end view of empty frond; e. transverse view.
