INJURIES INDUCED BY PLANTS 139 



spindle-shaped gonidia (Fig. 79, ), which at once germinate in 

 water, develop on the hymenial layer that lines the walls of the 

 cavities of these organs. 



Although I have watched the disease every year since 1885, 

 and have sought for the ascophores, I have hitherto been unable 

 to find them. I may, however, remark that in almost all my 

 cultures on silver fir branches a luxuriant growth of the 

 ascocarps of Peziza calycina has appeared upon the cortex on 

 both sides of the diseased part. This fact, however, is not 

 sufficient proof of a connection between 

 these two fungus-forms. Attempts to 

 produce the one form from the other 

 by cultural experiments have so far 

 proved abortive. 



The pycnidia ejaculate the gonidia 

 probably for the most part during wet 

 weather in summer and autumn. 



It does not appear necessary that FIG. 79. <*, a pycnidium 

 mechanical injury of the cortex should %? to $t 

 precede the entrance of the parasite magnified twenty times. 

 at all events, I have never been able m g e s nidia g nified 4* 

 to observe such. On old trees a large 



proportion of the twigs and branches are often brown, a state of 

 things that struck me at once on my first visit to the Bavarian 

 Forest. In the Black Forest also, and at several places in the 

 Bavarian Alps, the disease is to be met with. In the case of 

 the thicker branches nutrition through the wood may still be 

 continued for several years after the cortex has died. For this 

 reason growth in thickness above the dead part is distinctly 

 visible, and causes the cortex to rupture at the boundary of the 

 living and dead parts. When the wood covered by the dead 

 cortex dies and dries up, the passage of water ceases, and the 

 branch dies above the seat of the disease. 



Should the fungus attack one side of the branch only, the 

 dead cortex is exfoliated, and the formation of callus commences 

 along the healthy margin. 



