2 
DEVELOPMENT OF FORMS OF THE DISEASE, 19 
per cent of the galls ordinarily develop at the former point. An ex- 
ception occurs with some varieties, like the Wealthy, which are sus- 
ceptible to the hard form of crown-gall and woolly-knot. Such varie- 
ties often develop the disease from the scion above the union (PI. II, 
M23). 
It was found in experiments where the seedlings used for root graft- 
ing were carefully selected and only smooth roots used that hairy-root 
of the simple form was nearly eliminated. Such was not the case 
with the woolly-knot form. 
It is asserted by. practically all of the nurserymen from whom data 
have been collected, and the list includes nearly all of the large grow- 
ers of apples in the United States, that apple trees propagated by 
budding yearling transplanted seedlings are as a rule much freer from 
both crown-gall and hairy-root than root-grafted trees. 
Reports have been received from a number of nurseries giving the 
number of diseased trees among budded and root-grafted trees grown 
under similar conditions. These are combined and given in Table II, 
in the appendix. 
From Table II it will be noted that-there is a decrease of 3 to 
39 per cent of disease on budded trees as compared with root-grafted 
trees. Thisis representative of the reports received. Two exceptions 
not given in the table must be mentioned: One occurred in Utah, the 
other in Virginia. In these two instances budded trees were reported 
badly diseased with crown-gall. 
Under the conditions that generally prevail in the Central and 
possibly in the Eastern States, propagation by budding is advised at 
least in the case of varieties susceptible to erown-gall and woolly-knot. 
Owing to the fact that it takes one season longer to propagate an apple 
tree by budding than by root grafting, 1t will be more profitable to 
use the latter method of propagation in such States as California, 
where an apple tree is easily grown for market from root grafts in one 
season. 
RELATIVE DEVELOPMENT OF EACH FORM OF THE DISEASE IN THE 
NURSERY. 
Development on root-grafted trees—In all of the larger nursery 
experiments records were kept of the number of apple trees diseased 
with each form of crown-gall and hairy-root. In the set of experi- 
ments conducted on cooperative plats 1 to 8 (see p. 78), 50,472 
trees were grown from root grafts made from healthy scions and 
seedlings. Of these trees, 77.2 per cent was healthy, while 0.6 per cent 
was diseased with the soft form and 13.3 per cent with the hard form 
of crown-gall; with 2.6 per cent diseased with the simple form, 3.5 
per cent with the woolly-knot form, and 2.8 per cent with the broom- 
186 
