Sphinctospermum
hourglass peaseed, sphinctospermum
erect to ascending, young growth strigose.
alternate, unifoliolate;
stipules present, persistent;
sessile;
blade margins entire, surfaces glabrate.
solitary flowers, axillary, in leaf axils distally on branches;
bracts present, caducous, bracteoles absent.
papilionaceous;
calyx campanulate, lobes 5;
corolla pinkish;
stamens 10, diadelphous;
anthers basifixed;
style glabrous basally, with pollen brush uniform distally;
stigma terminal, capitate, ciliate.
legumes, sessile, laterally compressed, linear, elastically dehiscent, glabrous.
3–12, 4-angled;
with hilum recessed in a central constriction typically surrounding entire seed.
= 8.
Sphinctospermum
Species 1.
Sphinctospermum is native to the Sonoran Desert in Arizona and adjacent Mexico and to Pacific coastal dry forests in Mexico, including southern Baja California, where it is locally abundant but not often collected (M. Lavin 1990; Lavin and M. Sousa S. 1995).
Sphinctospermum is readily distinguished by its annual habit, unifoliolate, linear-lanceolate leaves, and solitary flowers measuring less than 10 mm. Such morphological distinctions greatly obscured the relationships of the genus until the advent of molecular phylogenetics (M. Lavin and J. J. Doyle 1991).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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