Flowerhead Anatomy and Major Types

64 • euDICoTS: asTeraceae SunflowerS: Family TraiTs

Flowerheads vary in form, foret composition, and type: Discoid, Radiant, and Disciform (all disk or sexuality. Some species have fowerheads with only disk-like forets), Radiate (disk and ray forets), and disk, disk-like, or ligulate forets; others have both Liguliforous (ligulate forets only). disk and ray forets in each fowerhead. Some species Cultivated members include western sunfower, have male and female reproductive parts in each foret safower, thistles, artichoke, tarragon, sages, European (bisexual), others have separate male and female chamomile, and chicory. With 23,000 species forets on the same plant, still others have entire worldwide and about 200 in our area, this is the largest plants with only male or female forets. We present family of eudicots and the second largest family of the asters in three groups based on their fowerhead vascular plants (second only to the orchid family).

Discoid Radiant Disciform Radiate Liguliforous

Florets Disk forets only A type of discoid Resemble discoid Disk forets in Ligulate forets head; disk forets heads; typically center, surrounded only only disk forets in by a ring of ray center, surrounded forets by fliform forets; fliform forets only in pistillate Baccharis heads Floret Size All forets Outer disk forets All forets All disk forets All forets about same-sized large, often about same-sized about same-sized about same- bilateral sized Floret Sex Each foret Each foret Disk forets (bisexual Disk forets Each foret bisexual (rarely bisexual or male) surrounded generally bisexual male-only with by tubular female bisexual, all fertile, sterile ovary, e.g., fliform or naked sometimes male; male forets of forets ray forets female Baccharis) or sterile Examples Artemisia Chaenactis, Artemisia californica Encelia Agoseris, tridentata, Cirsium, Lessingia; and A. douglasiana, (rays sterile), Malacothrix, Bebbia, Pluchea; Centaurea has Pseudognaphalium, Eriophyllum, Microseris, male forets of sterile outer forets female heads of Helianthus, Stephanomeria, Baccharis have a Baccharis Pentachaeta aurea, Tragopogon small sterile ovary true asters

Flowerhead Anatomy and Major Types

Paleae bracts on the receptacle, subtend florets Radiate Head Liguliforous Head disk and ray forets ligulate forets only Phyllaries flowerhead bracts, subtend the head, form the involucre Discoid Head disk florets only

Radiant Head Disciform Head disk forets; disk forets surrounded by outer large, fliform, naked, or sterile forets; roughly bilateral or all fliform or all naked

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