Notes 5 Oct.
- = Compositae
- The family is sometimes referred to as "the composites", which suggests the heads of flowers forming composite groups of tiny flowers.
- The sole member of the order Asterales.
- The second largest family of flowering plants. 23,000 species.
- See p. 84 (Walters & Keil) for key to major taxa (and subclasses of flowering plants)
- Many variations on several "themes"…
- Herbs, vines, some shrubs (in the tropics, many shrubs and trees)
- Lvs alternate, opposite, or whorled.
- Flowers of different kinds, always clustered in groups within capitula (= head).
Capitulum (head)…a more or less flattened, indeterminate (racemose) inflorescence.
- Youngest flowers in center, opening toward outside.
- Head is surrounded (before opening) by a series of involucral bracts. This series of bracts can collectively be called an "involucre".
- Involucral bracts may overlap (imbricated), or they may be side by side, with the margins touching. These bracts may be in a single series, or in two series, of if imbricated, in "several" series.
- All the flowers in the capitulum attach to the compound receptacle.
- Receptacular bracts are found in some genera/species. These are associated with individual flowers on the compound receptacle. Receptacular bract = "palea."
- Two basic kinds of flowers:
Ray flowers. Corolla of fused petals, forming a strap-shaped structure, sometimes lobed at the very tip. This corolla zygomorphic.
Disk flowers. Corolla is radially symmetrical, tubular.
- Ovary: always inferior…the flower parts are epigynous. Ovary made up of 2 carpels, ultimately only one ovule develops within. Ovary matures into an achene (fruit type), with a single seed inside.
- Calyx: represented by scales, bristles, or awns. See W&K p. 303. (In some genera/species, the pappus is absent.)
- Androecium: 5 stamens, epipetalous. The anthers tend to be marginally connate, forming a tube.
- Gynoecium (see above). The style pushes through the ring of anthers,. Two stigmatic branches separate at the apex of the style, when receptive to pollen.