18 BULLETIN" 365, U. S. DEPARTMENT OF AGRICULTURE. 
The present work includes the following 29 species of Del- 
phinium: D. ajacis L., D. andersonii Gray (National Herbarium 
No. 419245) , D. barbeyi Huth, D. bicolor Nutt., D. blochmannce Greene 
(National Herbarium No. 2060), D. calif omicum T. & G. (Na- 
tional Herbarium No. 419726), D. cardlnale Hook (National Her- 
barium No. 1928), D. carolinianum Walt. (National Herbarium No. 
442717), D. consolida, L., D. cucuMatum Aven Nelson, D. decorum 
F. & M. (National Herbarium No. 1939), D. depauperaium Nutt. 
(National Herbarium No. 529204), D. geranii 'folium Rydb. (Na- 
tional Herbarium No. 245524) , D. geyeri Greene, D. glaucum AYats., 
D. menziesii D. C. (National Herbarium No. 333235), D. nudicaule 
T. & G. (National Herbarium No. 612398), D. occidentale Wats. 
(National Herbarium No. 506615), D. recurvation Greene, D. 
robustum Eydb., D. sapellonis Ckll., D. scaposum Greene, D. scopu- 
lorum Gray (National Herbarium No. 234530), D. simplex Dougl. 
(National Herbarium No. 226416), D. tricorne Michx., D. trolliifo- 
lium Gray, Z>. variegatum Gray (National Herbarium No. 342458), 
D. variegatum apiculatum Greene (National Herbarium No. 1887), 
and D. virescens Nutt. 
These species were used, partly because they are the species which 
have been met in the field work on poisonous plants, and partly be- 
cause they were convenient to obtain for comparison. The specimens 
of barbeyi and menziesii were from fresh specimens which were fixed 
and embedded in the field, from specimens preserved in alcohol, and 
from dried specimens. The sections of sapellonis and cucullatum 
were from dried plants sent in from the field. The remaining speci- 
mens were from the United States National Herbarium, the Economic 
Herbarium of the Bureau of Plant Industry, and from the collection 
of Mr. Ivar Tidestrom. In addition to these species of Delphinium, 
stem sections were made of two species of Aconitum, for the purpose 
of comparison, since the two genera are very similar in structure, and 
since the two occur side by side in the field and both are suspected of 
poisoning stock. 
In preparing the dried herbarium material for sectioning it was 
treated with 2 per cent sodium hydroxid solution for 24 hours, or 
until the tissues were softened and swollen, then washed thoroughly 
in water, and put in a 10 per cent glycerin solution, the glycerin being 
gradually concentrated through a period of several days. The sec- 
tions were then cut in pith with a hand microtome, and stained with 
safranin. Perfect sections are not always obtained by using this 
method, but for the purpose of the identification of stems in field 
work it is preferable in most cases to embedding. 
Comparison of the different species was based solely on the char- 
acters appearing in the cross sections of stems. For each species 
