George Raymond Gage 11 



exceptional cases — that is, in very dry years — do the spores on the ovary 

 remain nngerminated. In these cases, however, they can play a certain 

 part in infection, even though a subordinate one. 



In addition to finding mycelium in the glumes and the stigma and 

 anther remains, Diehl found it in the lodicules and also observed that it 

 was vt ry abundant in the epidermis of the ovary. In the case of the 

 glumes and the epidermis of the caryopsis. long liyphae were produced. 

 Gemmae were formed in the stigma and anther remains, both from my- 

 celium and from sporidia. In the latter case the sporidia merely en- 

 larged and took on heavier walls. 



Diehl noticed also a considerable difference in the manner in which 

 blossoms opened for pollination. The blossoms of several varieties with 

 which he worked did not open ;it all. 



For the purpose of making tests of various disinfectants, Diehl re- 

 moved oat glumes, sterilized them, and inoculated them with spores, 

 thereby producing mycelium in them. He then returned these glumes 

 to the kernels. In a like manner, he inoculated and brought about inva- 

 sion of stamen remains and introduced these between the glumes. It is 

 evident from this that he does not consider the mycelium in the pericarp 

 as being very important. 



ROESCH 's STUDIES. 192 



Roesch (1926), the Latest of the Leipzig investigators cooperating on 

 the studies on oat smut, pursued methods similar to those of his cowork- 

 ers. His results and conclusions arc as follows: 



On the stigma, 100-per-cent germination of spores may take place. 

 On the epidermis of the caryopsis, the spores germinate very slowly and 

 giv( rise to only a few short hyphae. Ungerminated spores may be 

 found occasionally on the epidermis and the epidermal hairs of the 

 caryopsis. These do not play any significant role in infection, the rest- 

 ing mycelium and the gemmae on and in the remains of the stigma and 

 the stamens, in the glumes, in the caryopsis epidermis, and in the lodi- 

 cules, being concerned in the invasion of the seedling. 



With naked oats the invasion of the seedling takes place only by the 

 resting mycelium on the caryopsis epidermis, by gemmae, and, in iso- 

 lated cases, by overwintered spores. Additional infection may also re- 

 suh from spores which reach the oats at threshing time and which ger- 

 minate the next spring. Roesch considers that the pieces of stigma and 

 anther remains with mycelium and gemmae, which he found between 

 the epidermal hairs of naked oats, can play no important role in infec- 

 tion, since the hairs are broken off to a great extent during threshing. 



Roesch made studies of seedling invasion in the following manner: 

 Spores were germinated in a decoction of oat glumes. When there was 



