1*HE MONTHLY BULLETIN. 609 



On March 8, 1912, inoculations were made with this fungus, taken 

 directly from the bark and inserted into cuts in healthy trees. Pure 

 cultures were obtained from these diseased trees and used in later 

 inoculations.^ 



Figure 344 illustrates the result of an inoculation into the bark of a 

 healthy tree with grey fungus (Botrytis) , which had been taken directly 

 from diseased bark. The inoculation was made March 8, 1912. The 

 tree was photographed to illustrate the stage of the disease on July 13th. 

 Figure 345 shows the area of killed bark, outlined by a white mark, on 

 May 10, 1913, about one year and two months after inoculation. 



The bark of the tree shown in Figures 346 and 347 was also inoculated 

 with Botrytis fungus at the same time as Figure 344. It had begun to 

 gum by June 15th. It had gummed copiously during the summer of 

 1912, an area of bark six inches long and five inches wide being killed 

 by November. A ridge of gum five inches long and one and one half 

 inches wide had formed on the killed area at that time. The disease 

 appeared to be dormant during the fall, no new gum being formed, but 

 it began to spread again later. 



Figure 346 shows the outline of the diseased area of bark on Febru- 

 ary 22, 1913, and Figure 347 on May 10, 1913, showing how the areas 

 of infection have merged. A cut in the bark without inserting fungus 

 on the opposite side of this same tree has healed perfectly. A number 

 of other inoculations with the same fungus at the same time developed 

 similarly, while cuts in the opposite side of the same trees without fun- 

 gus healed perfectly. 



A few months later inoculations were made into the bark of healthy 

 trees with pure cultures of the grey fungus (Botrytis) which had been 

 isolated from the diseased bark of gummosis trees.^ The same type of 

 gummosis developed from these inoculations made with pure cultures 

 under careful control as had previously developed under less careful 

 conditions, but all kinds of injuries when kept sterile healed rapidly 

 without gumming. The outer part of the bark in inoculations with 

 Botrytis was killed first over large areas, the cambium remaining active 

 and alive for some time. When the fungus became quite active, espe- 

 cially during moist weather, the bark softened and died to the wool, and 

 the fungus produced raised cushion-like patches of grey spore-covered 

 bodies on the surface. In dry weather there was usually no visible 

 evidence of fungus. 



^In May, 1911, of the previous year Mr. R. S. Vaile and Mr. J. D. Culbertson had 

 inserted under the baric of healthy trees, bits of diseased bark showing a growth of 

 grey fungus upon it. Mr. Vaile's notes show that of five inoculations all produced 

 some gum in from three to six weeks, and that the fungus had developed most rapidly 

 on bark covered with neat's-foot oil. 



''It was a problem how to make inoculations or injuries into tree trunks in the 

 open and keep them free from organisms that might get in from the air or dust. 

 In attempting to overcome this difficulty the following method was adopted for the 

 most important of these inoculations : A cloth hood to be tied to the tree trunk was 

 made by fafetening a piece of fumigated tent cloth to a wooden barrel hoop cut open 

 on one side. Strings were fastened to the cut ends of the hoop and' to the corners of 

 the cloth opposite the hoop. The strings opposite the hoop were tied to the trunk of 

 the tree just below the branches and the hoop fastened below in such a way that it 

 caused the cloth to flare out and leave a place underneath protected from falling dust 

 and excessive currents of air. To settle the dust in dry weather the under surface 

 of the hood, the trunk of the tree and the soil about the base was sprayed with water. 

 The area of bark to be experimented" on was then washed first with water, then with 

 alcohol and quickly flamed with an alcohol lamp. The instruments used were either 

 sterilized by heat or by alcohol which had been allowed to evaporate from their sur- 

 faces. Some of the inoculations were protected by wax, some with oiled paper waxed 

 about the edges, and others with sterile microscopic glass slides held on with putty. 



