1906.] PUBLIC DOCUMENT No. 73. 129 



fungi. A later period of prolonged rain and dampness occurred 

 during the latter part of August and continued until September, 

 which was also the cause of a rather severe outbreak of parasitic 

 fungi affecting plants ; and I am informed by Mr. Ortou L. Clark, 

 who was at work in the parasitic laboratory at Maiden, that 

 numerous cases of the infested fall webs of the brown-tail moth 

 could be observed at Maiden, Wakefield, etc., during September 

 following this period of stormy weather and dampness. In this 

 case the white fungus covered the caterpillars located upon the 

 outside of the nests, apparently catching those which were more 

 subject to the inclemency of the weather at that period, since an 

 examination of the caterpillars in the nests at that time showed 

 them to be unaffected. 



In the course of our examination of the affected region, made 

 June 27, we obtained considerable material for microscopic study, 

 and material was sent to us at later date. We found most of 

 the external felt-like growths to be of a whitish color, which 

 proved upon microscopic examination to consist of fungous fila- 

 ments, and subsequently there occurred in most cases a reddish or 

 salmon-colored tint to the fungus. This was more especially noted 

 on the caterpillars which had been dead for a few days. Most of 

 the diseased pupae examined in the nests showed little or no fun- 

 gous growth, but after they collapsed the characteristic whitish 

 growth was evident. 



The result of our microscopic study of a number of dead cater- 

 pillars showed that there were two species of fungi present, one of 

 which will readily grow on agar (.1 per cent acid), and the other 

 will not. We had no difficulty, however, in isolating one of these 

 forms and obtaining pure cultures of the same. This proved to- 

 be the reddish or salmon-colored fungus noted above. It would 

 appear to grow very rapidly on agar, and would frequently cover 

 a petri dish in a few days. At first this fungus displayed a white 

 color, and then gradually passed into a light salmon or deeper red- 

 dish tint. The microscopic examination showed that it possessed 

 similar branching habits and spore formation to our common green 

 bread mold (Penicillium} , but in color it was entirely distinct 

 from this. From hanging drop cultures we were enabled to study 

 the fungus in detail and note its habits and the manner of forming 

 the spores. This fungus 1 proved to be a species of Penicilliwu, 



1 We are indebted to Prof. W. G. Farlow of Harvard University, whose criti- 

 cal knowledge and extensive herbarium are unexcelled, for the final identifica- 

 tion of this species. Professor Farlow compared the fungus with an authentic 

 specimen from Gosio, and found them to be identical. 



