24 THE CROWN-GALL AND HAIRY-ROOT OF THE APPLE TREE. 
piece roots from seedlings with smooth roots and one on piece roots 
from seedlings with hairy roots of the simple form. These were 
grown also in cooperative plats 1 to 8. Table VII, in the appendix, 
gives the combined results of the experiments. 
These experiments yielded three positive results: 
(1) The use of root pieces from hairy-rooted seedlings did not 
increase the amount of crown-gall, since in the two sets of experi- 
ments 7.3 and 2.6 per cent of crown-gall developed on trees grown 
from hairy-root pieces, as compared with 12.6 and 7.3 per cent, 
respectively, on trees grown from smooth-root pieces. 
(2) A greatly increased stand of trees resulted from the use of 
hairy-root pieces, since 4,956 trees were grown from grafts made on 
such pieces, as compared with 3,802 grown from the same number 
of grafts made with smooth-root pieces, an increase of 30.4 per cent. 
(3) The use of hairy-root pieces resulted in an increased number 
of trees diseased with hairy-root, since 77 and 83.7 per cent of the 
trees grown from grafts made with such pieces were diseased with 
hairy-root as compared with 10.2 and 8.9 per cent from grafts made 
with smooth-root pieces. 
The reason for the increased stand of trees from the root grafts on 
hairy-root pieces is as follows: Since the season was dry and unfa- 
vorable for the rooting of the grafts at the time of planting in the 
first experiments, the hairy-root grafts rooted more readily, and, as a 
results, fewer of them died and an increased stand resulted. The 
results of the following experiments are given in proof of this state- 
ment. It was found by a small experiment with cuttings from seed- 
lings diseased with simple hairy-root that 25 per cent of such cut- 
tings rooted (Pl. VII, fig. 1) and became trees in a bed in the green- 
house, whereas only 5 per cent of cuttings taken from smooth seed- 
lings of the same lot and planted in the same bed with the former 
cuttings took root, and then feebly. This experiment was made 
with 100 cuttings of each kind on an ordinary greenhouse bench 
with 8 inches of soil, without bottom heat. 
The trees grown from the different varieties of apples grafted on 
the hairy-root seedlings behaved differently in their root formation. 
Those varieties which rooted readily from the scion or stock—for 
example, the Fameuse and the Salome—sent out smooth roots, 
with very few exceptions, above the hairy-root piece (PI. VII, fig. 3). 
Such trees very often formed a well-balanced root system from the 
stock, and there followed the second year an atrophy of the hairy-root 
pieces, which did not injure the tree. In the case of varieties that 
did not root readily from the scion—for example, the Jonathan and 
the Scott Winter—most of the roots were poorly balanced and sprang 
from near the union (Pl. VII, fig. 4). On the whole, nearly two- 
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