52 Journal of Agricultural Research voi. x, No. i 



smuts and very likely more difficult to control. On the contrary, if its 

 recent prevalence has been due to very exceptional meteorological 

 factors, such as the warm weather in May and June of 191 5 associated 

 with frequent rains or heavy dews, then we may expect it to be much 

 less prevalent in years when these conditions do not prevail. I am 

 inclined to take a serious view of the situation because the disease 

 attacks not only the leaves, glumes, awns, rachis, and stalk of the wheat 

 plant, thus sapping the vigor of the whole plant, but sometimes also the 

 kernel itself, thereby suggesting (as already proved for maize attacked 

 by Bacterium stewarti) that it is carried over from year to year on the 

 seed. 



A careful study of the disease is under way in the I^aboratory of Plant 

 Pathology to determine the biology of the parasite and whether it is 

 actually transmitted from the seed to the young plant and so again to 

 the seed, as I suspect. I have also entered into cooperation with the 

 Kansas and the Wisconsin Experiment Stations for the further study of 

 this disease. This study will require considerable time, and it is desired 

 here only to call attention to some of the conspicuous signs of the disease 

 and to ask for samples of it from Station workers and others in all parts 

 of the United States, together with reports concerning its prevalence, 

 that we may know as speedily as possible its distribution and the extent 

 of the danger. 



The principal signs on the ripening grain are as follows : 



Chaff. — In late stages, as the wheat approaches maturity, black, lon- 

 gitudinal, parallel, more or less sunken stripes occur which, as a rule, are 

 more numerous and conspicuous on the upper parts, where they often 

 fuse, but which also often extend to the base of the glume. Internally, 

 in the parts corresponding to the stripes, the glumes are black- or brown- 

 spotted and swarming with bacteria, but sometimes, at least, fungi are 

 also present. In bearded wheat the beards are often attacked and 

 browned, at least in their basal parts. 



Rachis and stalk. — In late stages these are b'oth conspicuously brown- 

 or black-striped. 



Leaves. — In 191 5 I did not see the disease on the leaves, not many 

 leaves having been sent me, but from what I have seen this year I know 

 that they also are attacked (PI. 4, fig. 3). 



Kernels. — When t,he disease is serious, the kernels are badly shriv- 

 eled, and, in some cases at least, they show small cavities occupied by 

 bacteria. 



Whole plant. — The result of this disease is a dwarfing of the spike 

 and a very marked shriveling of the kernels, with corresponding reduc- 

 tion of the yield. 



Plate 4, figures i and 2, fr^m Kansas wheat (crop of 191 5) shows the 

 black striping on the glumes and rachis, and Plate 8 shows the common 

 shriveling of the kernels. 



