Last Addition: June 28, 1999
Each "thumbnail" image below is linked to a larger photograph.
Calycadenia spicata is a fairly common white-flowered species, mostly at elevations below 500 m on the eastern border of the Central Valley. It is often unbranched or sometimes sparsely branched from the base, rarely above. The exception is the form identified as "farnsworthianum" from the Greenhorn range at the southern extreme of the distribution of the species. This form fairly commonly branches above the base and also differs by having cream-colored flowers and rays with the lateral lobes broader and the sinuses shallower than in "spicata.". In both forms the peduncular bracts are distally terete, truncate, and have a single, impressed terminal tack-shaped gland. The chromosome number, n = 4, is the lowest in the genus. Natural interspecific hybridization involving this species is unknown. Experimentally, C. spicata has been hybridized with C. multiglandulosa, C. oppositifolia, and C. pauciflora (both n = 5 and n = 6 races).
|Comparison of greenhouse-grown progeny of "farnsworthianum" from the Greenhorn Range (left - note branching and see more striking example below) and "spicata" from Placer County (right -note more strictly spicate nature and essentially unbranched nature of each major axis - in the field there is often a single, unbranched, wand-like stem.|
|"spicata" 1 - Head in full flower, 2,3 - Heads in bud stage with surrounding peduncular bracts. Note peduncular bracts terete distally, the apex truncate and with a single impressed tack-shaped gland. 4 - Ray and disk florets. Note ray flowers deeply lobed and the lobes not as unequal as in "farnsworthianum."|
|"farnsworthianum" 1 - Greenhouse-grown progeny from Greenhorn Range population showing the unusual branching habit of this population, 2, 3 Closer view of heads and ray and disk florets. Note cream colored corollas and uneven lobing of the ray corollas. The fourth image is a head from a hybrid between the two forms.|
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