Systematics and palynology of Picrodendron: Further evidence for relationship with the Oldfieldioideae (Euphorbiaceae)

Abstract

ALTHOUGH KNOWN to botanical science for 285 years, the genus Picrodendron Planchon has been poorly understood for most of this time.The most pervasive problem has been that of discerning familial relationships, and there have been additional difficulties in typifying the generic name (Hayden & Reveal, 1980) and in distinguishing its three nominate species.This paper provides a systematic treatment for Picrodendron and demonstrates its relationships with Euphorbiaceae subfam.Oldfieldioideae Kéhler & Webster as evidenced by data on gross morphology, palynology, anatomy, and cytology.Picrodendron captured the attention of Dr. William T. Gillis while he was pursuing floristic studies of the Bahama Islands.During the decade preceding his death, Gillis accumulated a considerable amount of information on this problematic genus; he was attempting to complete this long-standing project in the weeks before he died in June, 1979.It has been a privilege tempered with sadness for one of us (W.J. H.) to prepare this paper from Gillis's notes and the contributions that he had solicited from the other authors.Herbarium and field studies reported here were performed by Gillis and form the basis for much of what appears in the generic description and the sections on biogeography and economic uses; taxonomic judgment at the species level is also Gillis's.Broome and Stone contributed descriptions of pollen and most of the discussion concerning the Juglandaceae