558 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM 
of natural crossing or are caused by other factors—a matter that is 
being investigated by Dr. Lyon. 
The mechanism of the flowers of C. bonariensis Lindl. is described 
and figured by Lindman (Bih. Svensk. Vet. Akad. Handl. 27: 
Afd. IIT. No, 14: 58. fig. 17. 1902). In southern Rio Grande do 
Sul, Brazil, the flowers are visited in December by very large 
bumblebees. The bee alights on the standard, usually about. hori- 
zontal in its reflexed position, and inserts its beak into the slit of the 
erect keel, which it spreads apart. The tip of the keel is thereby 
depressed and the anthers and stigma extended. 
SPECIFIC CHARACTERS. 
In the section Hucanavalia distinct species resemble each other so 
closely that often they can not be separated except by the mature 
pods and seeds. Unfortunately pods and seeds are often absent from 
herbarium specimens, so that the identification of such specimens is 
unsatisfactory. The seed characters in particular appear to be con- 
stant and reliable. Much of the confusion in botanical literature is 
doubtless due to the lack of mature pods and seeds on the specimens. 
SYSTEMATIC TREATMENT. 
CANAVALIA Adans. 
DESCRIPTON OF THE GENUS, 
Herbs or shrubs, mostly twining; leaves pinnately trifoliolate; petioles 
sulcate above; petiolules somewhat fleshy ; stipules caducous, thin, not striate; 
peduncles axillary; flowers numerous, in raceme-like thyrses, two or more short 
pedicels often arising from each prominent pedicellar gland; bracts minute, 
caducous; bracteoles mostly orbicular, caducous; calyx tubular-companulate, 
bilabiate, the upper lip large, bilobed, the lower small and simple or three- 
lobed; standard large, reflexed, with a pair of basal auricles and bearing two 
callosities toward the base; wings free, narrow, auricled ; keel falcate, truncate, 
the petals partly united; stamens monadelphous, the vexillar one partly or 
rarely entirely free; anthers all alike; style glabrous, rarely a little hairy 
near the tip; stigma capitate; pods stipitate, oblong or linear, beaked, straight 
or curved, compressed or turgid, the inner layer often loose and papery, the 
valves strengthened by one, two, three, or four longitudinal ribs, all very 
close to the sutures; seeds several to many, globose or ellipsoid and compressed, 
the hilum linear. 
Species about 40, all tropical or subtropical in both hemispheres, 
KEY TO THE SECTIONS. 
Pod valves each with one longitudinal ridge very near the ventral suture; 
leaves coriaceous; stems woody; seeds spherical or nearly so. 
1. Clementea (Clementea Cav.). 
Pod valves each with more than one longitudinal ridge; leaves membrana- 
ceous ; seeds ellipsoid, mostly compressed. 
Ridges two on each valve, one contiguous to each suture; stems woody. 
2. Diplegma. 
