8 
Colorado Experiment Station 
Under ordinary field conditions, a single pea plant branches at 
its base to form two or three principal vines. If the blight attacks 
and destroys one or more of these, the plant will usually throw out 
from three to five new ones, from the region below the diseased 
area, providing sufficient vitality remains to promote this growth. 
As a matter of fact, this is usually what takes place in the field, and, 
as a rule, the new growth progresses unmolested, altho, occasion¬ 
ally, this too is attacked. The secondary shoots are often small, 
and do not make the rank and vigorous growth that is character¬ 
istic of the earlier ones. 
If the vines become diseased when they are small, and the main 
vine dies before branching has taken place, the chances are that no 
branches will be formed, and the plant will be killed outright. 
Sometimes even the older plants behave in this manner. 
The leaves may develop the disease independently of any other 
structure and die before the stems show any trace of the trouble. 
Very rarely small droplets of a pale yellow exudate are found 
on the stems. 
The close resemblance in the appearance of alfalfa plants 
affected with the bacterial stem blight and that of diseased pea vines 
is a matter of considerable interest. In fact, the symptoms of the 
disease in the two plants are so similar as to justify one in making 
the conjecture that it is all one malady, and that one and the same 
causal agent is responsible for this condition. The pea and the 
alfalfa, both being legumes, and both grown in the same soil, under 
the same climatic conditions, and in a locality where the alfalfa 
blight has been very severe, the natural inference would be that 
both plants were suffering from the same cause. This is not the 
case, however, since the organism which we have isolated from the 
diseased pea vines and which we have been able to show is the 
specific cause of the pea trouble, is a separate and distinct form 
differing both morphologically and culturally from Ps. inedicaginis, 
the alfalfa blight organisnii. 
If fragments of the watery, olive-green tissue from either stem, 
leaf or petiole are mounted in a drop of water on a glass slide, there 
soon appears about the specimen a milky cloud easily visible to 
the naked eye. Under the low power of the microscope this resolves 
itself into a finely granular mass which flows out in all directions 
in long streamers, so characteristic of infections of this sort. 
Under the high power, the microorganisms which make up the milky 
cloud are readily distingaiishable as moderately motile rods from 
two to four times as long as broad. 
HISTOLOGY OP THE DISEASED TISSUE 
Celloidin sections of diseased stems, killed in absolute alcohol, 
show the substomatal chambers to be packed with bacteria and 
