THE MONTHLY BULLETIN. 611 



Figure 348 shows a lemon trunk that had been injured by a blow from 

 a crate hammer and then inoculated with spores of Botrytis and imme- 

 diately waxed over. A spot on the opposite side of this tree was cleansed 

 and pounded as on the side shown in Figure 348, and immediately waxed 

 over without inoculation. This was done July 11, 1912. The hammer 

 wound without fungus healed up without gumming. The inoculated 

 wound shown in Figure 348 was gumming slightly August 22d, and 

 copiously by September 24th. In the fall and winter it had stopped 

 gumming, and the area of killed bark remained small until the spring 

 of 1913, when it began to enlarge rapidly. The illustration (Figure 

 348), showing the area of killed outer bark outlined with chalk, was 

 taken May 10, 1913, ten months after inoculation. A recent examina- 

 tion of this bark showed that the greater part of the inner bark and 

 cambium was still alive under this killed area, and all but a few inches 

 of it will probably be saved by the method of treatment described later, 

 and illustrated by Figures 350 and 351. The application of pure neat's- 

 foot oil to injuries or cuts in the bark that had been purposely infected 

 with spores of the Botrytis fungus encouraged rather than hindered the 

 growth and development of the fungus. Neat's-foot oil applied to 

 sound pieces of bark placed in moist jars caused the Botrytis fungus to 

 grow in two weeks five times as fast as on bark without the oil. 



Brown Rot (Pythiacystis) Gummosis. 



In September, 1913, a fungus was isolated from another type of 

 gummosis at Whittier and inserted into the bark of trees at Santa Paula 

 in November. This has produced a form of gummosis which is, in all 

 respects, the same as that from which the fungus was isolated, and is 

 probably the most common form of gummosis in California. The bark 

 remains hard from the beginning, and is killed slowly all the way in 

 to the wood, without there being the least evidence to the unaided eye 

 or even through the hand lens of any fungus growth. 



Figure 349 illustrates by the different lines of chalk marks the 

 progress of the dying tissue from time to time. This tree was inoculated 

 November 23, 1912. The smallest outlined area represents the killed 

 area on February 12th, the next larger on March 14th, and the largest 

 area on May 6, 1913. The bark was cut off at the time this was taken. 

 May 6, 1913, to examine the condition underneath, and pure cultures 

 of the brown rot fungus were obtained from this bark. It was found 

 that in this case the killing of the inner bark lagged only a little behind 

 that of the outer bark and the bark was hard over the entire area. 

 These points appear to distinguish the brown rot (Pythiacystis) gum- 

 mosis from that due to the grey fungus (Botrytis) . Many other inocula- 

 tions had been made with cultures from brown rot infected lemons and 

 with bits of the infected lemons and typical cases of this form of gum- 

 mosis have resulted in every case. Clean cuts not inoculated made in 

 the opposite side of the same trees have healed up in the normal way 

 without exception. Cultures isolated from diseased bark and put in con- 

 tact with healthy lemons have produced brown rot, and cultures isolated 

 from brown rot lemons and put into the bark have produced in every 

 case this form of gummosis. Pure cultures of the brown rot fungus 

 (Pythiacystis citrophthora) have been isolated from gummosis bark 



