PLATE I. 
1B Es 
Ill. 
TV: 
Wal 
VALE: 
Vid: 
ILLUSTRA PIONS: 
Fig. 1.—Hard form of crown-gall of the apple. Fig. 2.—Woolly-knot 
Page. 
form. of hairy-root.of the apple) = 5 = Frontispiece. 
Fig. 1.—Soft form of crown-gall of the apple, from inoculation with 
rose galls. Fig. 2.—Soft form of crown-gall of the apple, from inoc- 
ulation with raspberry galls. Fig. 3.—Hard form of crown-gall on 
the scion portion of root-grafted apple trees. Fig. 4.—Hard form of 
crown-gall at the lower end of the scion in a root-grafted apple tree. 
Fig. 5.—Hard form of crown-gall surrounding the union in a root- 
erafted apple tree: 2.22, oa en Se SS eee 
Fig. 1.—Simple form of hairy-root on apple seedlings, typical of those 
used in the experiments. Fig. 2.—Broom-root form of hairy-root on 
a 2-year-old apple tree. Fig. 3.—Healthy root-grafted apple tree, 
showing the type of the healthy trees planted in the experimental 
orchards. Fig. 4.—Healthy seedling apple tree with fibrous roots. 
Fig. 1.—Early stage of the aerial form of hairy-root on an apple twig. 
Fig. 2.—Later stage of the aerial form of hairy-root on the same twig 
as that shown in figure 1. Fig. 3.—Early stage of the aerial form 
of hairy-root on an older limb of the same tree as that from which 
the twigs shown in figures 1 and 2 were taken...........---....-- 
. Fig. 1.—Mature stage of the aerial form of hairy-root on a Winesap 
seedling apple tree. Fig. 2.—Root production from the aerial form 
of hairy-root on a limb from the same tree as that from which the 
limb shown in figure © was:takencs. 422 o-etee ee 
Fig. 1.—Radial section through a soft crown-gall in an apple root 
graft. Fig. 2.—Early stage of the simple form of hairy-root on an 
apple seedling. Fig. 3.—A later stage in the development of the 
same form as that shown in figure 2. Fig. 4.—An older stage of the 
simple form of hairy-root, many roots being hair-like. Fig. 5.— 
Radial section through a woolly knot originating in a wound on the 
scion of a root-grafted apple tree. Fig. 6.—Radial section through 
a hard crown-gall originating on the lower end of the scion ofa 
root-grafted apple tree.) 2 S22 222 see ee 
Fig. 1.—Root of an apple tree grown from a cutting taken from a seed- 
ling apple tree diseased with the simple form of hairy-root. Fig. 2.— 
Root of a grafted apple tree grown from ascion taken from a diseased 
limb of the tree twigs and a limb of which are shown in Plate IV. 
Fig. 3.—Roots of a Fameuse apple tree grown from a root graft with 
the root piece diseased with hairy-root, but with healthy roots on 
the scion. Fig. 4.—Roots of a Jonathan apple tree grown from a 
root graft diseased with hairy-root, but with no roots on the scion. 
Fig. 1.—Apple root grafts showing nine kinds of wrapping used in the 
experiments. Fig. 2.—Root grafts left too long in storage, showing 
excessive development of callus. = 2-3 = = ee 
. Fig. 1.—The woolly-knot form of hairy-root on the crown of a Collins 
apple tree in orchard 1. Fig. 2.—Apple root grafts and seedlings 
used in the experimentg®: 22. (362 oe eee 
. Typical rows of trees in orchard 1: A, A row of Collins apple trees dis- 
eased with the hard form of crown-gall when planted in the orchard; 
B, a row of the same variety, planted at the same time, but with 
healthy roots... .. 2... 2 2S he See ee eee 
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