Calycadenia is a genus of 10 annual, mostly self-incompatible, aromatic species found primarily in and around the Central Valley of California. The genus is distinguished, in part, by the fascicled peduncular bracts, each with one or more prominent vascularized multicellular tack-shaped glands. Plants mostly 0.5 - 12 dm tall. Leaves alternate, at least above (all opposite in C. oppositifolia), narrow, linear, mostly basal (but these often deciduous by flowering time), reduced upward. Heads numerous, variously clustered, radiate; phyllaries (0)1-6, equaling the number of ray florets, partly enfolding the ray ovaries; ray flowers pistillate, the corollas 3-13 mm long, variously 3-lobed, white to rose or yellow, sometimes with a red spot near base; receptacular chaff peripheral, uniseriate, more or less strongly coalesced into a cup-like, false involucre; disk florets 1-25, perfect, the corollas 2-9 mm long, similar in coloration to the rays; anthers dark purple to black (except in rare mutants); cypselae dimorphic; ray cypselae thick-walled, more or less 3-angled with nearly flat inner surface and rounded to angled outer surface, epappose; disk cypselae thin-walled, straight, angled, base tapered, the pappus scales mostly 6-13 (rarely absent), generally more or less lanceolate, sometimes alternating long and short. Chromosome numbers of n = 4, 5, 6, and 7 are documented for the genus. Considerable infraspecific variation in chromosome structure is well documented in C. fremontii n = 6) and C. pauciflora (n = 5,6) and also occurs in C. truncata (n = 7).
Last Modification: November 25, 2006. Each "thumbnail" image below is linked to a larger photograph.
|Extensive biosystematic, cytogenetic studies of the genus Calycadenia were begun in 1970 at the University of California at Davis by G. D. Carr.|
|Most of the hybridization efforts on the genus since 1975 have been conducted at Eastern Washington University, Cheney, WA by R. L. Carr.|