CHESTNUT BARK DISEASE. 435 



that apparently enter into their success that we had not in mind 

 when the experiments were undertaken, namely: length of 

 time the fungus has been in artificial cultivation, age of the 

 particular spores used, and time of year of the inoculation. 

 This makes it difficult to judge of the results of certain of these 

 inoculations, since two or more of these factors may have been 

 involved. The final results of our inoculations were determined 

 about the second week in October. Of course this gave some 

 of the earlier inoculations made in May a much longer time to 

 develop than those made in July, although these latter had 

 plenty of time to show whether or not they were successful. We 

 will consider the results briefly under the following headings. 



Endothia gyrosa versus var. parasitica. Ordinarily it takes 

 about a month to determine whether or not an inoculation has 

 taken, and even then it is sometimes doubtful, since the tissues 

 around the wound often die back for a short distance as the 

 result of the mechanical injury. The sum total of our experi- 

 ments brings out quite clearly the difference in the parasitic 

 nature of these two fungi. For instance, 151 out of all of our 

 324 inoculations with var. parasitica, from all sources on all 

 hosts, produced more or less evident cankers, that is, 47 per 

 cent, were successful; while of the 148 similar inoculations with 

 E. gyrosa only 2 took, or about I per cent. Of these two, one 

 showed only a comparatively small dead area, with fruiting 

 pustules, around the point of inoculation, but did not seem to 

 continue its growth, while the other was on a dead seedling 

 whose roots had been cut off by mice, which no doubt weakened 

 it, allowing the fungus to make an excellent growth, and even 

 to produce its ascospores. If we take into consideration only 

 our inoculations of var. parasitica originally obtained from 

 chestnut and inoculated into chestnut sprouts and seedlings, we 

 find that out of 232 inoculations 132, or 57 per cent., took, as 

 compared with entire failure of E. gyrosa under the same con- 

 ditions. None of the 228 check trees in all our experiments 

 showed any signs of infection, thus proving that the wounding 

 alone was not harmful when protected from infection. 



With the check trees the cutting usually killed a little bark 

 on either side, especially if the knife was run under between 

 the bark and the wood. This never grew larger, and the callus 

 of new tissue formed in the wound was always healthy. With 



