Calycadenia micrantha R. L. Carr & G. D. Carr

Last Addition: November 25, 2006.

Each "thumbnail" image below is linked to a larger photograph.

Calycadenia micrantha occurs mostly in small colonies in the vicinity of Clear Lake, Lake Co., California.  A few additional populations occur in Trinity and Monterey Cos., California.  Like C. hooveri, C. micrantha is exceptional in being self-compatible; all other species of Calycadenia are strongly self-incompatible.  Calycadenia micrantha is found in very barren substrates at sites ranging from about 500-1500 meters in elevation.  Calycadenia micrantha is a self-compatible, diminutive derivative of the more robust widespread species, C. truncata, and differs from that species primarily in the reduction of structures correlated with the shift in breeding habit, e.g., ligule length (<3.5 mm vs mostly 5-12 mm), and disk floret number (1-3 vs mostly 5-25).  The chromosome number of C. micrantha is n = 7. Calycadenia  micrantha readily hybridizes with C. truncata in vitro but viable hybrid fruits are formed only on C. micrantha parents.

A -- Habit, B -- Capitulum, lateral view, C -- Capitulum from above, D -- Peduncular bract (appressed to capitulum, E  -- Ray cypselae, F -- Peduncular bract tip with tack-shaped gland. (from Holotype, R. L. Carr 3801 (UC).
cal_tru_sc_mids.jpg (11041 bytes) cal_tru_sc_hds.jpg (9593 bytes) cal_tru_sc_fls.jpg (10341 bytes)
1,2 - View of heads of greenhouse-grown plants from Lake County, 3 - Head of plant grown from fruits from Elk Mountain (Lake County), 4 - Ray and disk florets from progeny of Elk Mountain population, note small size of rays and rugose ray achenes.
cal_tru_scsis.jpg (11203 bytes) Comparison of heads of Calycadenia truncata (left) and the derived self-compatible species C. micrantha (right).

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