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. 



