153 



ticularly in the case of H. No. 17, given above, are to be regarded as fur- 

 ther saltation or as reversions. In all of these cases of sterile cultures 

 the mycelium, so far as can be judged, is like that of Helminthosporium, 

 but the colony-characters are altered in ways easily compatible with the 

 changes following loss of conidia-producing power and consequent change 

 in vegetative vigor. Ravn (91) mentions frequent sterility of cultures 

 in connection with Helminthosporium. 



H. No. 18, labeled H. avenae, gave conidia only once, on one wheat 

 shoot, although numerous trials were made. Its case is almost exactly 

 like that of H. No. 17. From the very few conidia, though inadequate, 

 Graph 98 (Fig. U) was made. 



H. No. 19, labeled "H. gramineum" rarely gave conidia under any 

 conditions, though somewhat more freely than either of the two preced- 

 ing numbers. (See Fig. U, Graph 99.) 



H. Nos. 13 and 14, labeled H. sativum, and Nos. 15 and 16, labeled 

 H. teres, are particularly interesting as showing variations in test-tube 

 culture. H. No. 13 is a lineal descendant of H. No. 14 while H. No. 16 

 is a similar descendant of H. No. 15. Graphs of these four strains also 

 are given in Fig. U (Nos. 93-96). It will be observed here that the differ- 

 ences between Nos. 15 and 16, which are separate cultures from the same 

 original isolation, are greater than the differences between strains known 

 to be quite distinct. Graphs of conidial breadth of H. Nos. 13, 14, 15, 

 and 16 are given in Fig. V. 



H. No. 20, labeled H. teres, appears to be an excellent example of 

 saltation in test-tube culture. It was so markedly different from other 

 cultures that during the several months in which I was ignorant of its 

 origin I thought that here was a clear case of difference between the Eu- 

 ropean and the American species. Subsequent word from Dr. Wester- 

 dijk advised me of the American origin of this strain, and that she had 

 received it in 1914 from Bakke, isolated from barley. It thus seems that 

 this culture from Dr. Westerdijk is a direct descendant of the culture on 

 which Pammel, King, and Bakke based their description (90), and that 

 it now differs markedly from that description as well as from a culture 

 (H. No. 3) which I received from Dr. Bakke which was also taken from 

 the same plots that gave the original culture and was regarded by Dr. 

 Bakke as being identical with H. sativum. Among my notes made before 

 I knew of the origin of the culture I find this memorandum: "H. No. 20 

 is quite distinct from all other forms in my cultures in its quite uniformly 

 6-septate conidium with its squarish middle cell. Its colony-characters 



