53 



(JROWTII ON OTHER MATERIALS THAN CHESTNUT. 



Ill the laboratory the I'uiigus i^rows well on a variety of artili- 

 cial media, perhaps most readily on i)otato agar that has been 

 made slightly acid. Material was submitted to us of white oak 

 and black oak bark, collected by Mr. J. li. Guyer, agent of the 

 Pennsylvania Commission, which bark had been killed by tire pre- 

 \ious to its observation, and siiitVsc . pustules of what seemed to 

 be Diaporthc parasitica. Careful microscopic examination show- 

 ed that the morphological feature's corresi)onded closely to those 

 of Duiporthe parasitica, as did also the growth of tlie fungous in 

 artificial culture, lied oak twigs killed by steaming in the process 

 of sterilization, were readily infected by Diaportlie jjarasitica ob- 

 tained from a typical chestnut lesion. AVhile it is desirable to 

 carry on further cross inoculation experiments, it seems rea- 

 sonable to suppose, in the light of present evidence, that Duipor- 

 tJiG parasitica mny, under unusual circumstances, establish itself 

 saprophytically on portions of trees outside the genus Castanea, 

 if these portions are already dead. We have found no evidence 

 that the fungus produces in any sense a disease of such trees us 

 the oak. 



RELATION TO LIOHTNING INJURY. 



In August, 1908, Mr. George Wirt, of the Pennsylvania For- 

 estry Department, directed the attention of the speaker to a 

 chestnut tree in an advanced stage of infection, that had been 

 struck by lightning earlier in the season, when its leaves were 

 half grown. Where the wood liad been splintered along the 

 lightning track, there were numerous pycnidia standing apart 

 one from the other, as is characteristic of Diaportlie parasitica 

 when fruiting on wood rather than on bark. Many of these fruit- 

 bodies were deep in the cracks nmde by the lightning, and evi- 

 dently had been formed after the stroke. Specimens taken from 

 the wood and from the bark near by, when tested, gave good 

 germination of sitores. rrobal»ly tlie l)ark infection, wliich 

 seemed to date far back, existed at llic lime of the stroke, and the 

 fungus S])r(M(l fi'(»m (Jiis to the sliat(ere<l wood, the lighdiing 

 presumably not having killed the fungus in the vicinity. 



