Today's photograph is courtesy of local field botanist Dr. Terry McIntosh. Terry took this image near Princeton, British Columbia in early September a couple years ago. Thank you!
Psilocarphus brevissimus has two recognized varieties: the Californian var. multiflorus and the far more widespread var. brevissimus. The latter can be found throughout western North America (see distribution map, but note incorrect absence from British Columbia), Baja California and parts of South America (Argentina and Chile). The reason for the disjunct (or widely separated) distribution isn't addressed in the resources I've read, but given the habitat requirements of the species, it can be imagined. Psilocarphus brevissimus is a species found along the drying margins of seasonally-inundated sites (like vernal pools and ditches). Long-distance seed dispersal via waterfowl or shorebirds seems the likely explanation.
Known commonly as short woollyheads or (my preference) woolly marbles, Psilocarphus brevissimus var. brevissimus is rare in some parts of its range, including British Columbia where it is a red-listed taxon restricted to the Princeton area. It is a low-growing annual, ranging from 2-10cm (1-4in.) tall.
Michael Charters' excellent California Plant Names: Latin and Greek Meanings and Derivations provides a meaning for Psilocarphus: the Greek psilos means "bare" or "naked" while karphos means "a splinter, twig, chaff, straw". This is in reference to the disk flowers in this genus not being subtended by chaffy scales (likely in comparison with a genus that is similar in appearance). The specific epithet means "very short" (same word root as "brevity").
A few additional photographs and illustrations are available via the Alberta Native Plant Council: Psilocarphus brevissimus var. brevissimus (PDF).