CHESTNUT BARK DISEASE. 437 



41 successful out of a total of 55, or 75 per cent., on the sprouts. 

 An attempt to inoculate a young Japanese chestnut six inches 

 in diameter failed entirely, although sixteen inoculations were 

 made at two different periods. This seems to show that the 

 tree had great resistance, if not immunity, to the disease. 



As regards inoculation of chestnut, versus oaks, it was found 

 that the former were much more readily infected than the latter, 

 which showed only 12 successful infections out of 51, or 23 

 per cent. All of these were confined to the sprouts, and did not 

 make nearly so vigorous growth as did the inoculations on 

 chestnut sprouts. The oak seedlings used were rather small, 

 and the inoculations were made comparatively late, using cultures 

 obtained originally from both oak and chestnut. 



Source of Cultures. Most of our inoculations were made 

 with cultures obtained from chestnut, as at the time we had only 

 one culture of var. parasitica from oak, namely Quercus velutina 

 from Woodmont, Pa. This was inoculated into both chestnut 

 and oak seedlings and sprouts. The inoculations into chestnut 

 seedlings showed 4 successful out of 25, or about 15 per cent., 

 while the 16 made on the chestnut sprouts all apparently failed, 

 for some not very evident reason, possibly because made in July 

 with old spores. Of the 20 inoculations on oak seedlings, all 

 failed, while of the 12 on oak sprouts, 5, or 42 per cent., took 

 more or less vigorously. From the results of the inoculations 

 with this single culture, it would seem that the strain from oak 

 at least was not quite so active a parasite as that from the 

 chestnut itself. 



Whether or not cultures from chestnuts from different regions, 

 or from living as compared with dead trees, show any difference 

 in virulence, we are not certain. In our experiments we did 

 not get any conclusive results along this line. To determine 

 these points accurately, however, one would need cultures that 



id only recently been obtained from their hosts, and whose 

 spores when used were comparatively young and of the same 

 ige. 



Age of Cultures. It seems quite probable that the longer the 

 variety parasitica is kept in culture the mere likely it is to lose, 

 it least in part, its virulence. While no direct experiments were 

 lade to determine this point, it is possibly shown by the cul- 

 tures obtained originally from a Japanese chestnut in Westville 



27 



