968 
Journal o f Agricultural Research 
Vol. XXXI, No. 10 
the resistant trees, as indicated by the scar of the healed injuries, 
were of a greater size than the galls that developed (pi. 2, B, and pi. 
3, A). On the susceptible trees the galls for the most part corre¬ 
spond in size with the scar of the healed inoculation (pi. 2, A). 
The formation of galls on this host can not always be correlated 
with growth activity. Negative results often take place on rapidly 
growing shoots. 
SOIL INOCULATIONS BY GALL FRAGMENTS 
The resistance of available nursery seedlings was tested in the 
manner already indicated, by inoculating the soil with fragments 
of galls at the time of planting. This method has been used by 
various investigators (7), and gave satisfactory results even before 
the true cause of the disease was known. It was employed as giving 
f )ossibly more normal conditions of infection. It would seem to be at 
east a more natural method than puncture inoculation in the twigs. 
Small, one-year-old trees were also inoculated by gall fragments in 
the same way as were the germinating pits. In most instances 
a much smaller percentage of galls was produced on the small trees 
by this method than by artificial inoculation in the twigs of the same 
species. Probably some other factors may have been responsible 
for this difference. The inoculum must be rather variable in its 
pathogenicity when broken fragments of galls are used, although care 
was taken to collect fresh galls and use them very soon after they were 
broken up. 
Table VII .—Results after two years 1 growth from germinating pits planted with 
minced peach galls 
Soil inoculated 
Soil not inoculated 
Stocks 
Number 
Number 
Number 
Number 
of trees 
with galls 
of trees 
with galls 
P. andersoni__ __ ___ 
17 
1 
6 
1 
Peach.... ..... 
30 
28 
32 
1 
Peach 0 __ _ _ ... 
29 
26 
42 
0 
Peach-almond hybrid (?)_____ _ 
52 
45 
34 
0 
Almond (hard-shell)..__ . 
57 
36 
42 
1 
Almond (bitter)_J:__ 
101. 
82 
78 
4 
Almond (sweet)________ 
98 
79 
42 
1 
Apricot (Royal)... __ ______ 
46 
22 
42 
0 
Apricot®___ ___ 
42 
16 
25 
2 
P. fremonti_ __ _ _»_ 
47 
18 
Almond (sweet)____ __ 
71 
49 
Peach.__ ____ 
47 
25 
Almond_ _ . __*L_ _ 
35 
25 
A. davidiana_ __ 
19 
11 
P. mume b _ __ 
16 
0 
Almond c _ ____ 
16 
10 
° Treated with Bordeaux paste. 
6 Trees examined, but not dug up. 
c As control on P. mume. 
USES OF RESISTANT STOCK 
A strongly resistant stock would have another use, in addition to 
that of propagating new trees. It could be used for inarching in 
orchards where the trees are already diseased with crown gall but 
not in too decadent condition. The inarching of small trees can 
