George Raymond Gage 27 



place will necessitate further study than has been made by the writer. 

 The observations of Roesch (1926:387) must be discounted, since his 

 methods are not in keeping with natural conditions. From the limited 

 investigations that have been made by the writer, it would seem that the 

 mycelium grows directly into the mesocotyl of the seedling. Since it is 

 difficult to section material and retain the epidermis of the pericarp in 

 place, a direct connection between a strand of mycelium in it and a 

 strand in the seedling has not been observed. On the other hand, (lie 

 very youngest seedlings in which mycelium could be detected were about 

 seven days old and the invading mycelium was found only in the meso 

 cotyl — that is. between the node from which the coleoptile develops and 

 the node from which the first roots arise. In seedlings a little older, from 

 twelve to fifteen days, mycelium was found in the coleoptile node and 

 also extending a short distance down into the roots. 



Should it be found that the mycelium grows out of the pericarp— 

 that is, that it develops on the outside of the caryopsis prior to its en- 

 trance into the seedling — then the pathogerie would have to be con 

 sidered as having a two-cycled life history. 



On examination of the culms of mature plants bearing smutted heads, 

 mycelium is seen to be most abundant in the nodal regions and in the 

 base of the leaf sheaths. It does not seem to favor any particular tissue. 

 being present in the parenchymal of the pith (Plate IV, 7) as well as in 

 that surrounding the vascular strands (Plate III, 5) and in that of the 

 leaf sheaths. In addition it is frequently present in the sclerenchyma 

 tous tissues (Plate III, 6). It is prevailingly intracellular, although 

 often found between the cells. This is contrary to the statements of Put 

 ler (1918:180) and Roesch (1926:389), but confirms those of Mc Al- 

 pine (1910:9). No true haustoria could be detected, [n the internodes 

 the mycelium is rather sparse and the hyphae are long and unbranched 

 In the nodes it is abundant and the hyphae are short, convoluted, and 

 much branced. There is no evidence of mycelial degeneration and dis 

 appearance in the older or lower parts of the culms, as stated by Butler 

 (1918:180). In fact the mycelium seems to be most abundant in tin 

 lowermost nodal regions. 



The mycelial invasion of the developing inflorescence and the forma 

 tion of ehlamydospores has not been studied by the writer. 



EPIPHYTOLOGICAL STUDIES 



The effect of temperature and moisture conditions was recognized 

 very early as having considerable influence upon the infection of oats 

 by these smut pathogenes. The difference in opinion as to whether low 

 temperatures or high temperatures favor seedling invasion is explained 

 by the recent work of Bartholomew and Jones (1923), from whose in- 



