This genus was described by Cassini (Bull. Soc. Philom. 1817: 10. 1817);
it belongs to the Vernonieae and is very close to Vernonia; the main difference is in
the outer pappus scales which are shorter than the inner ones and m a y be distinct
or connate in various ways; the inner scales are usually somewhat twisted; the achene
is always glabrous and 5-angled. Other characteristics make this genus recognizable
at first sight, such as the conspicuous dark round spot near the tip of the involucral
bracts and the glands near the tip of the corolla-lobes. Urban [Ark. Bot. 23A(11):
49-51. 1931] redescribed the only known species at that time, P rufescens Cassini,
and added a new species, P. antillana Urban. The Puerto Rican and Lesser AntiUean
specimens had previously been attributed to P. rufescens. However, examination of
the Bertero specimen in the Paris Herbarium, and of the Ekman collections in
Haiti left no doubt as to its identity; the other species is very different and was
described by Urban under P. antillana.
While studying the available herbarium material in the preparation of m y preliminary
survey of the Flora of Hispaniola, I found in the New York Botanical
Garden Herbarium a specimen collected by Ekman on the Samana Peninsula, which
was much different from the two known species. I described it as P. samancnsis
Alain (Brittonia 20: 153. 1968).
Another Ekman specimen from northern Santo Domingo was at that time considered
to be like a form of P rufescens Cassini, but with some reservations. My
own collections of P. rufescens, and further collections in the same E k m a n locality
together with other hitherto unexplored places lead m e to consider two more undescribed
taxa, and to revise the whole genus. Five species are included.