METHODS AND CONDITIONS OF EXPERIMENTATION. 79 
EXPERIMENTS IN ORCHARDS. 
Four orchards were planted with both healthy and diseased apple 
trees. These were situated on land owned or leased by the Depart- 
ment. They were located and designated as follows: 
Orchard 1 was located near Louisiana, Mo., on a gently sloping 
_ piece of upland consisting of a heavy clay loam. The land had been 
planted to grain and clover for twenty years. This orchard was 
planted to 208 apple trees. 
Orchard 2 was located on the same block of land as orchard 1, 
but it was lower and wetter in rainy seasons. It contained 261 apple 
trees. 
Orchard 3 was also located on the same block of land as orchard 1, 
but followed the trees grown in independent plat 1. It contained 
1,108 apple trees. 
Orchard 4 was first planted on the Potomac Flats, south of 
Washington, D. C., on built-up land from dredging, similar to that 
in independent plat 3. The 500 apple trees in this orchard after 
one year were transplanted to a block of land with a colluvial- clay 
loam on the Arlington Experimental Farm, in Virginia, where they 
are now located. 
The trees for planting in these orchards were selected as follows: 
Healthy, vigorous, 2-year-old apple trees with a well-balanced root 
system of smooth roots (PI. III, fig. 3) were selected in each experi- 
ment for a check or control. To test the effects of the forms of 
disease there were selected sets of trees of the same varieties, of 
equal size, and from the same stock of trees, some of which were 
diseased with crown-gall (Pl. I, fig. 1) and others with hairy-root 
(Pl. I, fig. 2). All of the trees used in the experiments were selected 
by the writer. Both healthy and diseased trees were planted and 
tended equally well. 
All of the data on these orchard and nursery experiments were 
personally recorded by the writer, notes being taken on each indi- 
vidual tree. 
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