170 



Mycologia 



In the autumn of 1907, diseased leaves were enclosed in wii;e 

 nets and placed out of doors to winter. Being located in Louisi- 

 ana in the spring of 1908, Mr. C. J. Humphrey, of the Botanical 

 Department of Cornell University, kindly sent me the leaves from 

 the nets, and also others picked up from under the affected white 

 poplar trees. The leaves were received during the last part of 



Figs. 1-5. Asci, spores, and paraphyses of Trochila Populorum. X 750. 

 I. Mature asci. 2. An ascus, showing how the apex is ruptured when the 

 spores are thrown out. 3. Ascospores. 4. Germinating ascospores. 5. Para- 

 physes and young asci. 



April and May. In nearly all of the spots on nearly all of the 

 leaves, there was an abundant development of an ascomycete 

 which I determined as Trochila Populorum. Many attempts 

 were made to culture the ascospores in 1908, but without success. 

 The spores would not grow in acid media, and, in dilution cul- 

 tures using ordinary media, bacteria and molds ruined the plates. 



