962 
Journal of Agricultural Research 
Vol. XXXI, No. 10 
The introduction P. armeniaca (S. P. I. 32834) also seems promising, 
but has not been sufficiently tested. 
The varieties of the European plum ( Prunus domestica) are placed 
together in Table II. This species contains a great diversity of 
varieties, some very resistant and others rather susceptible. Six of 
the seventeen tested show 15 per cent or less of galls developing from 
artificial inoculations. Is this what may be expected when a number 
of different varieties of a species are tested by artificial inoculations? 
P. insititia, the damson group, is in many respects very similar to 
P. domestica . It shows a very satisfactory resistance. 
Table II .—Artificial puncture inoculations on varieties of Prunus domestica, 
arranged in order of resistance 
Variety 
Source a 
Number 
of inocu¬ 
lations 
Number 
of galls 
Per cent 
of galls 
Italian Prune __ _____ __ __ _ 
NF_ 
340 
13 
3.8 
Golden Drop __ ____ _ _ _ __ _ __ 
NF_ 
160 
14 
8.7 
German Prune _ ___ __ _ __ 
NF_ 
350 
31 
8.8 
Washington. _ _ _ ___ 
NC_ 
60 
6 
10.0 
President __ _ __ . . _ _____ 
NC_ 
140 
19 
13.5 
Giant__ _ _ __ 
NC_ 
60 
9 
15.0 
P. D. stock b ___ __ __ _ _ 
NT_ 
420 
77 
18.3 
Columbia__ _______ 
NC_ 
80 
20 
25.0 
Black Damask_ __ 
NLC_ 
20 
6 
30.0 
Reine Claude (Green Gage).. _ _______ 
NF_ 
160 
62 
32.5 
Sergeant__ __1_ __ 
NC_ 
130 
49 
37.7 
Red Magnum Bonum (Red Egg)____ 
NF_ 
80 
26 
38.7 
Jefferson _ ... __ __ __ . ___ 
NC_ 
110 
49 
44.5 
St. Martin _ ____ 
NC_ 
130 
81 
62.3 
Grand Duke _ __ _ _ 
NC_ 
60 
42 
70.0 
Bartlett __ _____ 
NC_ 
60 
51 
85.0 
Sugar . _ _ _ 
NF_ 
70 
67 
95.7 
a The explanation of the letters used in Tables I, II, and VIII may be found under “ Source of material.” 
6 Stock of Prunus domestica , used to a limited extent in California. This material was obtained as 
suckers from orchard trees budded or grafted on this root. The stock can be propagated rather easily 
by root cuttings. 
SOME RESISTANT SPECIES 
The species showing marked resistance are listed in Table III, and, 
with the exception of Prunus ilicifolia , P. caroliniana, and P. serotina , 
merit further field tests as stocks for the stone fruits. Some of them 
have been used in a limited way, while others probably have never 
been given experimental trial as stocks. 
Table III .—Species of Prunus and Amygdalus showing less than 16 per cent infec¬ 
tion by artificial inoculations with pure cultures of Pseudomonas tumefaciens 
Species 
i 
Common name 
Number 
of inocu¬ 
lations 
Number 
of galls 
Per cent 
infection 
P. illicifolia.. _ . __ 
Holly-leaf cherry_ . 
150 
0 
0.0 
P. caroliniana _ 
Cherry-laurel_„ _ 
150 
0 
0.0 
P. pumila 
Sand cherry__ 
450 
1 
0.2 
P. iimhfillfl.tR 
Black sloe____ 
150 
1 
0.6 
P. domestica ° 
Italian prune_ - - . 
340 
13 
3.8 
P. alleghaniensis _ _ ' . 
Allegheny plum__ __ 
250 
12 
4.8 
A. tangutica.. -- __ 
Chinese wild almond_ 
430 
25 
5.8 
P. mume - .. _ 
Japanese apricot. _ 
4,950 
307 
6.0 
P. domestica.. ._ _ .. 
Golden Drop plum_ 
160 
14 
8.7 
P. domftstififl. 
German prune.__ 
350 
31 
8.8 
P. bfissfiyi . _ _ 
Sand cherry_1_ 
280 
29 
10.4 
P. insititia. _ ___ 
St. Julian plum.. .... 
110 
11 
10. C 
P. sfirotina, _ _ _ 
Black cherry___ 
150 
21 
14. C 
P. insititia _ .... 
Shropshire plum___ 
230 
35 
15.2 
a Only one of the six varities listed in Table II as showing 16 per cent or less infection is given here. 
