86 MISSOURI BOTANICAL GARDEN. 
Vermont State University, Ohio University, Iowa Agricul- 
tural College, and Florida Agricultural College; and while 
in Philadelphia for a few hours in 1898, I made a hasty 
examination of the herbarium of the Philadelphia Academy 
of Sciences. My thanks are due to those who have kindly 
permitted me to examine the collections in their charge and 
to many others who have sent smaller collections or speci- 
mens from various parts of the country; and especially to 
Dr. Wm. Trelease, at whose suggestion the work was taken 
up, for every possible facility and kindness in carrying on 
the work at the Garden and securing for my examination 
the collections from the larger herbaria of the country. 
Aside from recording what has come to light in a study 
of the material accumulated in herbaria from the many col- 
lections of the thirty-seven years since the last revision, it 
is hoped that the present monograph may at least have 
some value in collecting the isolated descriptions, and put- 
ting in more accessible form our knowledge regarding this 
group of plants; and that it may be some aid to future 
students of Euphorbia. 
In general I have followed the system of classification 
used by Boissier, and, with little modification, by the prin- 
cipal systematists since his time. The subsections are left 
practically as he defines them, with the exception of Ipeca- . 
cuanhae which is modified by the removal of FH. Ipecacu- 
anha L., its relative Z. gracilis Ell. and /. trichotoma HBK. 
The first two must be excluded from Tithymalus because 
of the presence of distinct though minute stipules, and 
very narrow but usually evident glandular appendages. 
E.. trichotoma is placed in the subsection Hsulae because 
of the carunculate seeds. Some slight rearrangement of the 
species in the subsections has been made, which I believe 
will better indicate the natural relationships. 
The section Tithymalus comprises the greater part of 
the known species of Euphorbia, containing nearly 400 of 
the 700 or more described. Comparatively few occur in 
2 
rn ot a OEY of 
