VIII PREFACE 
new genus is somewhat intermediate in character between Baccharis 
and Conyza .(Eschenbachia) and its recognition materially clarifies 
the generic relationships in its group. 
The final paper of the volume (part 14), entitled The American 
Species of Canavalia and Wenderothia, was suggested by the con- 
fusion discovered by Professor Piper in this group of plants while 
he was studying their economic possibilities. A paper dealing with 
the Old World species, by C. V. Piper and S. T. Dunn, was published 
in the Bulletin of the Royal Botanic Gardens, Kew, in 1922. In 
studying the American species Professor Piper has had access to all 
the material in American herbaria, besides that at Kew, including 
nearly all the types. The genus Wenderothia of Schlechtendal has 
been restored, 12 species being recognized, one of which is new. In 
Canavalia there are 26 species in 4 sections, 13 being new. The 
economic importance of the group is not great. Canavalia gladiata 
is widely but rather sparingly cultivated in the tropics and sub- 
tropics, the seeds being used as food. C. ensiformis is employed as 
a green manure crop, and the seeds, occasionally eaten, are now the 
commercial source of urease. C. campylocarpa is used in the West 
Indies as a green manure crop. 
FREDERICK V. COvVILLE, 
Curator of the United States National Herbarwum. 
