IMMUNITY PEACH ON PLUM. 41 



The peach upon plum were not set in a body, but were scattered among 

 the large trees. 



I saw them the last of May, 1890, at which date they looked more 

 promising than either of the other plantations. They were reexamined 

 October 11, 1891), but many were choked and overgrown by weeds so as 

 to be scarcely visible. Part of them had also been injuriously shaded 

 by the older trees. Some were dead and very few had made a satisfac- 

 tory growth, but none were suffering from yellows. Their bad appear- 

 ance was attributable in part to neglect. Young trees set into older 

 orchards require special care. 



(c) The remainder of the trees 75 Mountain Kose, 100 Crawford's 

 Late, and 107 Crawford's Early were set on Dr. W. S. Maxwell's farm, 

 at the mouth of Sassafras Eiver, Kent County, Maryland. The 2 

 acres selected for this orchard are on a level hilltop, overlooking or- 

 chards No. 1 and No. 18 of my first report. This field seemed very well 

 adapted to the experiment, having been already once in orchard and 

 being in the center of a region of diseased orchards. The remnants of 

 the first orchard, about 75 trees in all stages of yellows, were re- 

 moved in the spring of 1890. They were then 9 years old, i. 0., set 9 

 years, arid were the last to become affected. The rest of the trees had 

 succumbed earlier and were dug out at various times, most of them in 

 1888. The trees had grown vigorously and were large. 



The peaches on plum roots were received November 7 and were set 

 the same day, midway between the places occupied by the old trees. 

 Three-fourths of these trees were very fine ; the rest were small. They 

 were set shallow with a view to lessening the attacks of borers. 



About one pound of unleached, hardwood ashes was distributed 

 around each tree at planting, and tomatoes with phosphate were grown 

 in the field in the summer of 1890. 



The black peach aphis appeared upon the tops of these trees in early 

 spring, and destroyed many of them. The remainder were seen as late 

 as the last of May and then promised well. 



These trees were reexamined October 8, 1890. At that time 88 were 

 dead, mostly from the attacks of the black aphis. Of the remainder, 

 42 were stunted and yellowish like similar trees in Mr. Greene's orchard, 

 while 152 were very thrifty and still bore dark-green foliage. In the 

 former, in every ca^e, the peach top had overgrown the plum stock, 

 producing a distinct bulge. In the latter the stocks had kept even 

 pace with the growth of the tops, and the abundant foliage was still 

 vigorous. In fact I have seldom seen finer yearling trees. Photos 1 

 and 2, plate xxvii, were made October 18 from representative trees of 

 each group. None of these trees showed any signs of yellows. 



The five trees which furnished the buds were reexamined very care- 

 fully July 22, 1891, i. e., 3 years from the beginning of the experiment. 

 They were still entirely free from yellows, or any symptoms suggestive 

 of that disease, and were more vigorous than in 1890, owing to the 

 turning under of a crop of scarlet clover. 



