18 THE CROWN-GALL AND HAIRY-ROOT OF THE APPLE TREE. 
under ordinary nursery conditions. One-half of the trees, taking 
alternate trees in each row, were dug at the end of one year after 
transplanting, and the remaining trees at the end of two years. In 
transplanting, the taproot of each seedling was cut off. Table I, in 
the appendix to this bulletin, gives the results of the experiment. 
Twenty trees died from the effects of transplanting. It will be 
noted in Table I that there was an increase of crown-gall amounting 
to 0.8 per cent the first year and 0.1 per cent the second year after 
transplanting. At the same time there was an increase of 8.6 per 
cent of hairy-root the first year, and a decrease of 2.3 per cent the 
second year. 
No experiment was made with seedlings grown from seed in which 
the trees were allowed to grow in the original place of planting for 
longer than a year. Nurserymen assert that there is little or no 
increase of disease after the first year, and that where seedling trees 
have been pulled with a tree puller at the age of 10 years in the 
seedling nursery there is no greater percentage of disease present 
than during the first year. : 
RELATIVE DEVELOPMENT OF THE DISEASE ON BUDDED AND ROOT- 
GRAFTED TREES IN THE NURSERY. 
Development on budded trees.—In the propagation of varieties of 
apple trees by budding, seedlings at-the age of 1 year are tipped; 
that is, the taproot is cut off. Then they are planted in rows in the 
nursery. These are budded the following summer. The slit in the 
bark where the bud is inserted is just above the surface of the soil. 
Crown-gall of both forms usually develops, if at all, at the two points 
where wounds are made, i. e., at the place where the bud was 
inserted and at the tip of the root. As arule, much less crown-gall 
develops on trees propagated by budding than on those propagated 
by root grafting. Hairy-root develops more frequently than crown- 
gall on budded apple trees. The simple and the woolly-knot forms 
are common, the former developing on portions of the root below 
the surface of the ground and the latter at or near the surface, often 
from the region of the wound made in budding. 
Development on root-grafted trees—In the propagation of apple 
trees by root grafting, whether by whole roct or piece root, more 
extensive wounds are necessarily made than are usual in budding. 
Wounds occur at the point of union where the scion piece is spliced 
to the root piece—at the lower end of the scion piece and at the upper 
and lower ends of the root piece. 
Crown-gall, both soft and hard, like callus, develops usually at two 
points in the root graft—the lower end or tip of the scion piece (PE 
VI, figs. 1 and 6) and the lower end of one root piece. More than 90 
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