notes Only a small clump of plants was seen briefly here late in the day...wish there had been more time to photograph & study it in the field (and search for more!).This is a fascinating taxon...considered the most highly-developed of the three members of what was circumscribed as ''section Neoxtheca'' in Barbara Ertter's excellent 1980 revision of Oxtheca (1st page from JSTOR here). The section Neoxtheca was later elevated to generic status as Sidotheca by Jim Reveal in 2004.
As part of the distinctive morphology here, the 5-awned funnelform involucres are laterally-compressed ('taco'-like ;-) with a narrow whitish margin, and are densely stalked-glandular on the adaxial surface. There are 3-6 flowers within each involucre, with the major portion of the relatively elongate perianths included within the taco-like involucre and only the tips of the 6 perianth lobes ('tepals') exserted beyond the involucral edge. Those tepal-tips are laciniate with the 3-5 lacinia baso-laterally fringed and apico-centrally elongate-attenuate.
I could not find a freely-accessible link to the entirety of Ertter's 1980 revision, but a treatment of Sidotheca by Reveal can be read here (scroll to bottom of page for the discussion of species emarginata). The original 1902 description of the species by H. M. Hall (as Oxytheca emaraginata) can be read here (figures on Plate 14 here...but note the perianth lobe tips are not very accurately rendered in Fig. 2 there).
