22 THE CROWN-GALL AND HAIRY-ROOT OF THE APPLE TREE. 
appendix, in which all forms of disease, both crown-gall and hairy- 
root, are combined. A large increase of hairy-root, but not of crown- 
gall, was noted the second year. | 
The second experiment was made with five varieties, Northwestern 
Greening, Grimes, Duchess, Walbridge, and Ben Davis, grafted on 
seedling roots of the same stock. The same number of grafts of each 
variety was made in two equal sets, one with scions 6 inches and 
piece roots 4 inches in length, the other with scions 4 inches and roots 
6 inchesin length. The former were planted with the union 5 inches 
below the surface of the ground, and the latter with the union 3 inches 
below the surface. An equal number of each set and of each variety 
were planted in cooperative plats 1 to 8 (see p. 78). A definite 
proportion of the trees, selected in a numerical series in the rows, was 
dug each year for three years, at the ages of 1, 2, and 3 years, respec- 
tively. The results are shown in Table IV, in the appendix, in which 
the number of trees and the percentage diseased with crown-gall and 
hairy-root are given. 
From the results of these two experiments (see Tables III and IV) 
it will be noted that there was an actual increase of the disease in the 
case of the shallower planting of the union, in the first experiment 
amounting to 6.5 per cent and in the second to 2.5 per cent. The 
greatest development of crown-gall took place the first year and of 
hairy-root the first and second years. If the results of the two 
experiments be combined by adding the number of healthy and 
diseased trees in each, the result is 19.2 per cent of diseased trees 
where the union was planted deeper and 22.2 per cent where planted 
shallower, or a difference of 3 per cent in favor of the deeper planting 
of the union. This, however, is much more than offset and the 
practical results of the experiment are reversed by the fact that 13.2 
per cent more trees were raised when planted shallowly than when 
planted deeply, or, in other words, there was a gain of 10.2 per cent 
by planting the union 24 to 3 inches below the surface of the soil as 
compared with planting it 5 to 6 inches deep. 
The slight effect from using different portions of seedling roots in root 
grafting.—In making piece-root grafts the root of the seedling tree is 
cut into two or more pieces. The opinion has been expressed by 
nurserymen that when the upper or collar piece of the seedling root 
is jomed to a scion in a root graft there will be a greater prevalence 
of disease than when the lower or middle piece is used. In order to 
test this assumption a series of experiments was conducted in which 
equal numbers of grafts were made on the collar or upper pieces of 
the seedling roots and on the tip or lower pieces of the roots. Scions 
from five varieties of apples—Northwestern Greening, Walbridge, 
Grimes, Duchess, and Ben Davis—were used. These were grown in 
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