In the winter of 1950, Drs. Maguire, Wurdack, and Cowan collected in Venezuela a leguminous plant which at the time v/as of unknown affinity generically and until this year it remained so. This winter, duplicates of the collections of this plant were sent to Mr. N. Y. Sandwith, who kindly studied it and suggested that it was to be associated with the genus Dicymbe. He also compared some of the types in this genus; for this assistance I am very grateful.
With the recognition of the relationship of that plant, several other collections proved to represent still other new species of the genus. In the light of these additions, it seems wise to present a preliminary treatment of the genus.
It is evident that in this group we are confronted with another of the reduction series which seem almost characteristic of this part of the Caesalpinioideae; the problem to resolve is the status to be accorded each of the stages of the series. The corolla is more involved in this group than any of the other flower parts. In sect. Dicymbe the corolla is composed of five, equal or subequal, petals; sect. Triplopetala, as the name implies, is characterized by three complete petals and two petalodia; in sect. Eremopetala four of the five petals are reduced to petalodia but the fifth has a well-developed blade; and the species of sect. Apoxypetala have all the petals reduced to subulate-lanceolate petalodia. In spite of the obvious differences between the extremes of this reduction series, I feel that the phylogeny of the group is better expressed by treating it as one genus, consisting of two subgenera, each with two sections.
Of the four sections recognized, three require names and they have been named with Greek compounds signifying the petal condition of each group. Eremopetala refers to the single, "lonely" petal; Apoxypetala refers to the absence of complete petals, that is, the petals are "reduced"; and Triplopetala refers to the three complete petals of the one species included here. This is the species formerly referred to Dicymbopsis by Ducke and ordinarily the generic name would be used as a infrageneric epithet but here it is impossible, according to paragraph four of Article 31 of the Rules; the sectional name must not repeat the generic name with the ending "-opsis."
The keys to the species in each of the sections is followed by notes on each
of the species and citations of specimens seen; in all cases, only collections
represented at the New York Botanical Garden are cited. There has been no
attempt to arrange the species phylogenetically, but the related species are
grouped together. Latin diagnoses to validate the subgenera and sections will be
found in the part dealing with the species.