A Stem Blight of Field and Garden Peas 
31 
18. EFFECT OF GERMICIDES.— This has been reserved for a 
future publication. 
IV. PATHOGENICITY 
Pathogenic to field peas (Pisum sativum var. arvense) and 
garden peas {Pisum sativum). Not pathogenic to alfalfa {Medi- 
cago sativa), sweet clover—yellow— {Melilotus officinalis), crim¬ 
son clover {Trifolium incaratum), mammoth clover {Trifolium 
pratense, var. perenne), cow peas {Vigna unguiculata), and garden 
beans {Phaseolus vulgaris). 
V. GROUP NUMBER 
Ps. 21 1.2322033 
FIELD EXPERIMENTS 
In conjunction with Mr. E. H. Thomas, of Alamosa, we have 
endeavored to study the progress of the disease in the field under 
natural conditions. To this end, Mr. Thomas staked and marked 
25 field pea plants, most of which were affected, on June 12, 1915,* 
on the ranch of Mr. W. F. Ulray between Monte Vista and Center. 
These were observed at frequent intervals during the early 
summer, and changes in their condition from time to time were 
recorded as given in Table VI. The disease was most active from 
June 12 to June 17; on June 24 it had made but little further 
progress, and by July i it had practically disappeared. 
Briefly, our study of these plants has brought out three points: 
First, badly affected shoots, where.the infection is within a few 
nodes of the growing tip, are almost invariably killed outright; 
second, as a rule, when the original shoots are killed, new ones come 
up to replace them, except in very young plants; third, if the infec¬ 
tion is confined to a few internodes next to the ground, the shoot 
outlives the disease and its growth is undisturbed. 
