PEACH YELLOWS AND PEACH ROSETTE. 



173 



A number of the unbudded trees at one end of the orchard died in the 

 spring of 1890 from some unknown cause, not yellows. They dried up 

 suddenly, much as if they had been injured by plowing or by moles. The 

 root's, however, seemed intact and the origin of the trouble was not to be 

 learned in July. It is sufficient that it was not yellows or anything sug- 

 gestive of that disease. Four of the trees set on sod ground also dried up 

 during the summer. All the rest of these trees (86) made an excellent 

 growth in 1890 and were thrifty and beautiful to look upon.* 



For several reasons this experiment is more interesting than No. 1, 

 although the results are identical. First, the inserted buds were taken 

 from shoots that appeared to be healthy; second, the disease developed 

 more slowly than in Experiment 1, owing probably to the different char- 

 acter of the buds; third, a smaller amount of infective material was 

 used; fourth, the inception and progress of the disease occurred in a 

 locality entirely free from yellows. This experiment confirms No. 1. In 

 addition, it proves that yellows may be communicated by parts of a tree 

 which seem to be healthy, and renders it probable that the disease is 

 incubating in all parts of a tree when it appears in any part. In passing, 

 it may be said that the results of the excision experiments described in 

 Part III point to the same conclusion. It is also noteworthy that each 

 of these trees was infected by a single bud, and that all of these buds were 

 cut from a single tree. The inference is very strong that this one tree 

 contained infective material sufficient to destroy entire orchards if prop- 

 erly introduced into the trees. Both experiments go to show that the 

 germ or virus of the disease must be quite uniformly distributed through 

 the affected parts. 



Experiments 3 and 4 (the R. G. Nicholson trees and the D! P. Bar>ard 

 trees) are' incomplete, owing to the temporary discontinuance of this 

 investigation in the spring of 1888. 



At the time of removal Mr. Barnard reserved ten trees from experiment 

 4, and set them with others of the same age in an orchard on his farm. 

 According to his statement, January 10, 1889, they made a good growth in 

 1888 and were healthy as any trees. September 20, 1890, Mr. Barnard 

 reported that the trees were still healthy, but they were not personally 

 inspected until January 26, 1891. 



At that date the following conditions prevailed: One tree was gone; one 

 tree had made no growth worth mentioning and was dead with symptoms 

 of yellows; three were much smaller than should be and were suffering from 

 yellows or at least presented what seemed to me satisfactory symptoms; 

 one was doubtful; and four were nice trees. The latter had made a reason- 



* These trees were re-examined Augast 12, 1891, with the following results: 



Average height of the north two rows (37 trees), 9.9 feet; average circumference of trunk, 8 inches. 

 Average height of the south three rows (19 trees), 8.1 feet; average circumference of trunk, 5.7 inches. 

 Twelve of the trees have mildewed badly this year, one has yellows, and several others are small, Other- 

 wise all are healthy and growing vigorously. The difference in amount of growth is referable to the unlike 

 methods of treatment. They have been cultivated with crops as follows: 



The growth of a crop of wheat in 1889 and the absence of cultivation the following year, when the trees 

 were in clover sod, checked the growth of the south three rows nearly one third. Of the inoculated trees 

 only six remain, and they are like the three left from Experiment 1. 



