52 THE CROWN-GALL AND HAIRY-ROOT OF THE APPLE TREE. 
experiments varied from 1.2 to 41.7 per cent and of hairy-root from 
1.8 to 6 per cent. 
(2) The use of carefully fitted root grafts, as compared to poorly 
fitted ones in both experiments, yielded an increased stand of trees. 
This increase amounted to 21.6 per cent in the first experiment and 
to 26.7 per cent in the second experiment. This was due to the 
death of many more of the poorly fitted grafts just after planting, 
before they struck roots. 
In the case of the smoothly fitted grafts the superior stand of trees 
is due to the more perfect union formed by the callus quickly estab- 
lishing a circulation in the graft when it is planted in moist soil. 
This brings about a more rapid healing and results in a higher vitality 
and an increased stand of trees. 
A poor fitting of root grafts also causes an increase of abnormal 
callus, permitting a greater communicability of crown-gall during 
the first year’s growth. This increase takes place chiefly at the time 
the wounds of the graft union are healing. The same does not apply 
so well to forms of hairy-root, which, as a rule, are not necessarily con- 
nected with the graft union, but occur as often on other portions of 
the roots of grafted trees. 
What does this loss from poorly fitted root grafts mean to the 
nurseryman? On the basis of 15,000 trees to the acre, a low estimate, 
it means the loss of 2,355 marketable trees for every acre of apple 
trees. If trees are valued at 8 cents apiece, it means the loss of 
$188.40 per acre. 
The use of scions from diseased trees uncreases the amount of disease.— 
It has been the custom of some growers of grafted apple trees in the 
central United States to grow their stock three years before market- 
ing it. The yearling trees are cut back to near the ground, and the 
tops are used for scions in making root grafts for the next season’s 
planting. A portion of such scions must, of course, come from trees 
with diseased roots. Some growers cut scions directly from cull 
trees in the nursery bins, many of which are diseased with crown- 
gall and hairy-root. Others plant these culls in their scion orchards 
and later cut scions from them. ‘These three methods of selecting 
scions must be condemned, since they tend to increase the number 
of diseased trees grown from orchard grafts. 
In order to test the effect of taking scions from trees with diseased 
roots, a series of experiments has been conducted, in which scions 
were taken from trees with both healthy and diseased roots. 
The grafts in the first and largest experiment were planted in 1905. 
The trees were dug in 1906, at the age of 2 years. In this experi- 
ment the trees used were grown from root grafts made in equal number 
from scions taken from healthy trees and from those diseased with 
186 
