168 



opinion that the disease was due to Helminthosporium teres. It may be 

 remarked here that Ravn (91) says that leaves are the only substrata on 

 which conidia are developed ; which is certainly a marked distinction from 

 the H. sativum group which sporulate so freely on agar of many kinds. 



There is no question whatever in my mind that by meaira of biometry 

 and a study of biologic relations and cultural characters, tenable distinctive 

 diagnoses can be drawn up for many races of Helminthosporium on the five 

 leading cereals. How many of these should be designated by binomials and 

 how many left unnamed appears, on final analysis, to be a question of the 

 utility of such naming, which, in turn, may hinge upon their economic or 

 other importance rather than upon the magnitude of their morphological 

 or other differences. 



H. No. 20 is particularly interesting in that it is if no error exists in 

 its history an example of saltation so great as to remove the organism 

 entirely from the group under discussion (the forms with tapering conidia), 

 and consequently to place it in a group (Linneon) different from that to 

 which its known relatives (H. Nos. 13 and 14) belong. 



CONCLUSION 



The present study was undertaken with two leading objects: (1) to 

 determine the efficient cause of the rotting at the lower part of the wheat 

 stem ; and (2) to throw light on questions of morphology and parasitology 

 in the genus Helminthosporium. The questions arising from saltation 

 injected an additional interesting series of observations. The evidence is 

 complete that Helminthosporium can and does cause foot-rot at the base 

 of wheat stems. The study has also shown the Helminthosporium (H. 

 No. 1) to be a root parasite. This phase of the disease has been studied 

 only incidentally, but it is worthy of searching investigation since it may 

 lead to the resetting often associated with foot-rot, and thus predispose 

 the plant to foot-rot. 



SUMMARY 



1. In the rotting base of the wheat a Helminthosporium is the only 

 organism constantly present (p. 124). 



2. The culture characters of this fungus were studied on many me- 

 dia (p. 79) and under many and various environmental conditions. Slight 

 changes of nutriment, as afforded by small differences in agar formulae or 

 by the temperature at which the agar was made, produced marked effect 

 on growth-characters. Of many agars tried, corn-meal agar proved most 

 useful. Cereal shoots autoclaved, served as a still more favorable medium. 



