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Habit: dioecious palmlike shrubs with erect, aerial, cylindrical stems, with many leaves. Leaf-bases shedding or persistent. New leaves emerging in flushes.
Leaves: pinnate, spirally arranged, interspersed with cataphylls, lower leaflets not reduced to spines. Petiole spine-free. Rachis not twisted. Longitudinal ptyxis erect, horizontal ptyxis erect. Leaflets simple, with numerous parallel veins and no distinct midrib, leaflets inserted along the adaxial midline of the rhachis; leaflets lacking a distinct basal callosity; epidermal cells elongated obliquely or transversely to long axes of leaflets. Leaves pubescent, at least when young, with branched or simple transparent trichomes.
Microsporophylls: spirally aggregated into determinate, sessile male cones and each with a simple sterile apex, with a deflexed broadly triangular termination. Each microsporophyll bearing numerous microsporangia (pollen-sacs) on its abaxial surfaces. Microsporangia opening by slits. Pollen cymbiform, monosulcate.
Megasporophylls: spirally aggregated into determinate, sessile female cones. Sporophylls simple, appearing peltate with a simple dilated apex or lamina with a deflexed broadly triangular apical termination. Ovules two (rarely three), sessile, orthotropous, inserted on the inner (axisfacing) surface of the thickened lamina and directed inwards ("inverted").
Seeds: subglobular to oblong or ellipsoidal, with a red outer sarcotesta. Endosperm haploid, derived from the female gametophyte. Embryo straight; with 2 cotyledons that are usually united at the tips and a very long, spirally twisted suspensor. Seeds radiospermic; germination cryptocotular.
| The Cycad Pages © 1998 Royal Botanic Gardens Sydney Written and maintained by Ken Hill Please send comments and corrections |