April, 1906.] Ascochyta pisi — Disease of Seed Peas. 
507 
Finally some winter buds show a very distinct vernation— 
conduplicate, involute, revolute, plicate, or convolute — although 
this is usually well shown only while the leaves are expanding 
in the spring. The conduplicate vernation is very distinct in 
the winter buds of Liriodendron tulipifera and the involute ar- 
rangement in the buds of Populus balsamifera. 
ASCOCHYTA PISI,— A DISEASE OF SEED PEAS.* 
J. M. Van Hook. 
During the season of 1904 and 1905, there was an exceptional 
blighting* of peas from Ascochyta pisi Lib. The disease was 
general throughout the state and occasioned loss especially 
where peas are grown in large areas for canning purposes. 
My attention was first called to this trouble June 24, 1904, on 
French June field peas, which had been sown with oats as a for- 
age crop. Most of the peas at this time, were about two feet 
high and just beginning to bloom. The lower leaves were, for 
the most part, dead. A feW plants were wilting after several 
days of sunshine following continuous wet weather. Other 
stunted peas grew among these, some of which never attained a 
height greater than a few inches. 
Appearance on stems, leaves, pods and seed . — A close examina- 
tion of the plants showed that the stems had been attacked at 
many points, frequently as high as one and one-half feet from 
the ground, though most severely near the ground where the 
disease starts. In the beginning, dead areas were formed on 
the stem in the form of oval or elongated lesions. At a point, 
from the top of the ground to two or three inches above the 
ground, these lesions were so numerous and had spread so rapidly 
as to become continuous, leaving the stem encircled by a dead 
area. In some cases, the woody part of the stem was also dead, 
though the greater number of such plants still remained green 
above. This was due to the excessive amount of moisture in 
the soil and atmosphere previous to this time. On the leaves, 
were orbicular or oval dead spots, one-fourth to one cm. in diam- 
eter. These areas are darker at the circumference. Below, 
the leaves were badly spotted, causing them to die. In the 
greenhouse, the spotting of leaves failed to develop, though the 
attack at germination and at the base of the stem was more 
severe than out of doors. The dead areas at the base never ex- 
tend much above the surface. Such plants as are not killed 
1. Presented at the Cincinnati meeting, Ohio State Academy of Science. 
2, The disease has been erroneously termed “Club root” by canners, since, on exam- 
ining the roots for cause of dying, nodules common to members of the family Leguminosae, 
have been observed. 
