Edgerton : Trochila populorum Desm. 



171 



In the season of 1909, material was again sent me from Ithaca, 

 and further attempts were made to culture the spores, though 

 by a different method. The affected leaves were placed in a 

 moist chamber and petri dishes containing sterile agar were in- 

 verted over them. As the apothecia opened up, the spores were 

 shot out of the asci into the agar above. These spores germi- 

 nated and I was able to transfer them to tubes. The germ-tube 

 was sent out either from the side or at the end of the spore 



{fig- 4)- 



On sterilized bean pods and alfalfa stems, the fungus grew very 

 slowly, finally forming a colony from one to two millimeters in 

 diameter, when all growth ceased. The tubes were kept for nearly 

 a year, some of them being transferred to see if further growth 

 could be obtained. The cultures were examined occasionally, but 

 I was never able to find any two-celled spores in them, being 

 similar in this respect to Potebnia's cultures from the Marssonia 

 spores themselves. As the cultures were made in Louisiana, per- 

 haps the high temperature had much to do with the lack of 

 development of the spores. Not being able to find the spores in 

 the cultures, I was not able to prove absolutely the connection 

 between the Marssonia and the Trochila; but from the fact that 

 the Trochila always developed in the Marssonia spots, and also 

 from the somewhat similar colonies in pure culture, with the 

 exception of spore formation, it seems very probable that the 

 two forms are connected. 



In a letter from Dr. E. J. Durand, he states that Trochila 

 Populorum has never been found in America, so far as he knows. 

 This being the case, perhaps a short description may not be out 

 of place. 



The apothecia are at first somewhat globose, but as they grow 

 older they generally become more or less flattened and concave at 

 the top {fig. 6). The upper portion of the apothecium is forced 

 out of the leaf during its growth, so that at maturity it projects 

 some little distance from the surface of the leaf. The outer 

 layer of the apothecium is composed of a. pseudo-parenchymatous 

 tissue of a dark-brown color. Inside of this, there is a more 

 delicate layer of hyaline cells. The outer layer entirely surrounds 

 the developing asci and paraphyses and is not broken apart at the 

 top until the ascospores are nearly mature. In size, the apothecia 



