NEMATODE DISEASE OF WHEAT. 29 



wheat, although apparently not to so great a degree. Further care- 

 ful observations in the field and more adequate cross-inoculation 

 experiments are necessary, however, in order definitely to deter- 

 mine the relation of the nematode to these cereals. 



On many wild grasses, flower galls due to species of nematodes 

 closely related to and by many believed to be identical with Tylen- 

 chus tritici have been found by both European and American ob- 

 servers. Bessey (4) in 1905, for example, reported that he had 

 found such galls in grasses of the genera Chaetochloa, Agropyron, 

 Elymus, Calamagrostis, and Trisetum collected in Texas, Oregon, 

 and Alaska, but was unable to determine whether any of them were 

 induced by an eelworm identical with the wheat nematode. Some in- 

 vestigators have given the causal organism occurring on the various 

 grasses specific names, such as Tylenchus agrostidis, T. graminearum, 

 and T. phalaridis, depending largely upon the host attacked, and 

 sometimes in the brief inadequate description of these parasites the 

 writers have pointed out minor differences between them and Tylen- 

 chus tritici. On morphological grounds alone these described dif- 

 ferences are not sufficient to warrant separating them from the wheat 

 nematode, and for this reason Dujardin (13), Diesing (12), and 

 Bastian (2) in their helminthological monographs have considered 

 them identical with Tylenchus tritici.. Whether the gall-producing 

 nematodes discovered on different grasses are physiologically alike 

 in parasitism can, of course, be determined only by cross-inocula- 

 tion experiments, a thing which the above-mentioned investigators 

 apparently did not attempt. Marcinowski (22), however, in an ex- 

 periment covering two years, failed to induce flower infection of 

 many grasses with Tylenchus tritici. Each plant during the first 

 year was inoculated with the larvae of several hundred wheat galls 

 and during the next year was again treated with the larval content of 

 about 300 galls. The grasses used in the experiment were, for the 

 most part, those on which galls had been reported. They are as 

 follows : 



Agrostis capillaris, A. stolonifera, A. canina. 



Bromus erectus, B. pratensis, B. secalinus. 



Alopecurus gemculatus. 



Festuca ovina, F. pratensis, F. vulgaris. 



Holcus lanatus. 



Boa annua, F. pratensis. 



Phleum bohmeri, P. pratense. 



Although suspicious symptoms appeared in the leaves during the 

 second year on Festuca vulgaris, Poa annua, and Alopecurus genic- 

 ulars, not a single gall was found on any of these hosts, and the 

 fruit matured normally. 



