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 means 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 rosetting 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. 
