152 



Mycologia 



Every peach tree on which the bark had been cut and a bit of 

 fungus inserted, began to gum in from four to seven days, the 

 tissue near the point of inoculation gradually dying. In no case 

 were any of the trees killed ; but in one instance the cambium on 

 one side of the stalk was killed to a distance of seven and one half 

 inches from the inoculated point, and pycnidia of the Diplodia 

 were produced along the deadened area sixteen days after the 

 inoculation. In most cases the gum oozed out in tough, irregular 

 masses one half to three fourths of an inch across, and remained 

 attached, not only at the point of inoculation, but at other points 

 on the bark. In one instance a mass of gum was formed six 

 inches from the point of inoculation. One inoculation was made 

 by slightly scraping the outer bark and placing on it a bit of 

 mycelium. In this case gumming also occurred. Other inocula- 

 tions were made by placing bits of the mycelium in contact with 

 uninjured bark of different ages. Where the twigs were tender 

 and green, gum was induced, but where branches were older no 

 infection took place. 



In no case did the check trees exude any gum, and the cuts 

 which had been made gradually healed up in the normal way. 



Orange trees were also inoculated, in the same manner as 

 described for the peach trees, with cultures isolated from citrus 

 trees. In nearly every case a flow of gum was produced, which 

 was more watery than that of the peach, but in time hardened 

 into large tear-like drops below the point of inoculation. 



The orange trees kept as checks, which had been cut and 

 wrapped in the same way as the inoculated trees, failed in every 

 instance to produce gum, and the cuts gradually healed up in the 

 regular way. 



Cross inoculations were finally made in which the peach Diplo-- 

 dia was introduced into cuts in orange trees, and the citrus 

 Diplodia was introduced into cuts in the bark of peach trees. The 

 result was that gumming was produced in every case, in the same 

 way as previously described. 



Cultures of this fungus were again isolated from these inocu- 

 lated peach and orange trees, and these cultures showed the same 

 features of growth as those from which the inoculation had been 

 made. As far as known to the writers, this is the first time that 



