2 i6 
Journal of Agricultural Research 
Vol. XXIV, No. 3 
below so as to cause the cloth to flare outward and thus protect the wound 
from falling dust and excessive currents of air. In order to prevent 
dust in dry weather, the under surface of the hood, the trunk, and the soil 
around the base of the tree were sprayed with water. The area of bark 
to be experimented on was washed, first with water and then with alcohol, 
and quickly flamed with an alcohol lamp. The augers, hammers, 
knives, or other instruments used were sterilized either by heat or by 
alcohol which was allowed to evaporate from their surfaces. Either 
grafting wax or glass slides sealed with putty were used as a covering in 
most of the experiments. 
There was no gum exudation or development of disease in connection 
with any of the experiments with which attempts were made to keep the 
bark free from contaminations. With the experiments in which spores of 
Botrytis cinerea were used as a contamination, however (except where 
the bark was not injured) gum exuded, and in most cases typical Botrytis 
gummosis lesions developed around the place of injury. 
The results of these experiments appeared to show that injuries were 
not sufficient in themselves to induce gum diseases. When the injuries 
were contaminated with pure cultures of Botrytis cinerea^ however, under 
the same conditions, gum formation and death of the tissue were readily 
produced. 
Inoculations with Pure Cultures of Botrytis cinerea 
Many inoculations have been made with pure cultures of Botrytis 
cinerea and the following is typical of the results. 
On July 12, 1912, spores and sporophores of Botrytis cinerea were 
inserted in a cut 2.5 cm. long, on the trunk of an 18-year-old lemon tree 
at Santa Paula. The wound was then covered with oiled paper. Gum 
was exuding rapidly by July 20 and continued to do so until a diseased 
area 4 by 5 cm. was noted on August 22. On November 21, there was a 
softened, dead area of bark, 15 by 5 cm., which on February 14,1913, was 
23 by flcm. in size and on June 27, 1913, 28 by 10 cm., with new gum, and 
Botrytis fruiting on a part of the surface. On July 28, 1913, the main 
area was 32 by 10 cm., and a number of smaller areas were scattered over 
the same side of the trunk. On scraping the trunk for treatment at this 
time, it was found that only a small area of bark was killed through to the 
wood, only the outer cortical layer of the remaining part being dead. 
Bordeaux paste was applied to one lateral half of the scraped portion. On 
November 25, 1913, the disease was seen to be arrested on the portion 
treated with Bordeaux, but further dying of outer bark had taken place 
on the other portion. A similar cut without inoculum made on the oppo¬ 
site side of same tree healed without gumming or any other apparent 
effect. 
In all, about 40 inoculations with pure cultures of Botrytis cinerea were 
made on lemon trees, most of which resulted in gummosis of the ty]>e 
represented by the previous example. The general results of a number of 
these are given in Table XIII. 
