Asteridae: Campanulales. The Campanulaceae are herbs, shrubs, or rarely small trees comprising about 70 genera and 2,000 species usually with milky sap. The leaves are nearly always alternate and simple; stipules are absent The flowers are bisexual, and actinomorphic in the subfamily Campanuloideae but zygomorphic in the Lobelioideae. The perianth and androecium are usually 5-merous, sometimes 3-10-merous. The calyx and corolla each consist of connate segments. The stamens equal the number of corolla lobes, alternate with them, and are adnate to the extreme base of the corolla or epigynous zone or more commonly arise from the annular epigynous nectary disk; the filaments are distinct and the anthers are introrse and only weakly connivent around the style in the Campanuloideae but in the lobelioideae the introrse anthers and also often the filaments are firmly connate. The gynoecium consists of a single compound pistil of usually 2 carpels and locules with numerous axile ovules in the subfamily Lobelioideae but usually consists of 3-5 carpels and locules with numerous axile ovules in the subfamily Campanuloideae. The single style commonly has a number of lobes or stigmas equal to the number of carpels. The ovary is nearly always inferior and is generally crowned with an epigynous annular nectary disk. The fruit is usually a capsule or berry.
Each "thumbnail" image below is linked to a larger photograph.
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Platycodon grandiflorum, balloon flower (Campanuloideae). Notice the actinomorphic, 5-merous nature of the open flower and the inferior ovary of the old flowers in the background. This is a good example of a protandrous flower, one that has the androecium maturing before the gynoecium. The stamens that were earlier connivent around the style have now spread apart and are beginning to shed pollen. The stigmatic lobes are still firmly pressed together with the receptive surfaces unavailable for pollination. These lobes would spread apart and expose the receptive surfaces in the next phase of maturation of the flower. Protrandry is one mechanism that inhibits self pollination in plants. | ||
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Wallenbergia ? (Campanuloideae). The stigmatic lobes have separated in this flower. Notice the withered stamens and the actinomorphic nature of the flower. | ||
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Comparison of subfamilies Campanuloideae and Lobelioideae. On the left a cross section of a typical ovary in the subfamily Lobelioideae shows 2 locules and numerous axile ovules. On the right is a typical ovary of the Campanuloideae with 5 locules and numerous axile ovules. The cut surfaces show some evidence of milky sap. | ||
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Lobelia cardinalis, cardinal flower (Lobelioideae). This is a typical flower of the lobelioid subfamily showing a 2-lipped, zygomorphic corolla and an inferior ovary. Notice the tubular filament and anther column from which style and stigmatic lobes have emerged. As the style elongates through this column, hairs on the outside of the tightly closed stigmatic lobes brush the pollen that is released to the interior out the top of the anther column where it is available for removal by biotic pollinators. | ||
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Lobelia gaudichaudii (Lobelioideae). This endemic Hawaiian species is found on summit ridges of the Koolau Mts., O'ahu. | ||
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Delissea subcordata (Lobelioideae). This species represents one of the endemic Hawaiian genera of lobelioids. | ||
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Clermontia kakeana, 'oha (Lobelioideae). This Hawaiian endemic lobelioid genus includes freely branched shrubs and small trees. | ||
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Cyanea pinnatifida, haha (Lobelioideae). This Hawaiian endemic lobelioid genus includes shrubs or trees with mostly candelabra-like growth forms. | ||
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Brighamia insignis, alula (Lobelioideae). This rare and unusual cabbage-like Hawaiian endemic lobelioid is found only on nearly vertical cliff faces of Kaua'i and Ni'ihau. |
