310 Robinson and Walkdcn.—A Critical Study of Crown Crall. 
The gall was then washed in running water for about four hours (thus 
attempting to wash off as many organisms as possible from the surface), 
then placed in a second tube of sterile water for ten minutes ; finally the 
gall was cut into small pieces with a sterile scalpel, and dropped into 
a further io c.c. of water for ten minutes. Platings were then made, using 
for each plate a loopful of the water from one of the three tubes. The 
experiment was carried out with a number of actively growing galls from 
five to eight weeks old, and the results of some such tests are summarized 
in Table I. 
Table I. 
Platings made to test the number of Bacterium tumefaciens on the exterior 
and interior of galls, and also the possibility of washing galls free from 
B. tumefaciens. 
A. 
B. 
c. 
Gall placed for io min. 
Same gall, after washing 
Same gall cut into small 
in io c.c, 
. sterile water. 
in running water for 
pieces 
and placed in 
about 4 hours, placed in 
10 c.c. sterile water. 
10 c c. 
sterile water. 
Age of gall. 
No. 
of 
PL 
... , » py act. 
1 otal , 
, , . tumc- 
b act ena. s ■ 
jaciens. 
% 
rr . , / P} dot. 
Total 
, . . tumc- 
bactena. r ■ 
jaciens. 
rr, , 7 P aCt . 
Total 
z , . tume- 
badena. s • 
jacie 7 is 
Six weeks 
i. 
>—< 
•^r 
00 
54 
3 ° 
12 1 
9 
5 
2. 
333 
122 
37 
13 3 
12 
3 
3 - 
192 
62 
32 
15 6 
0 
O 
0 
4 - 
212 
89 
42 
1 5 
8 
5 - 
164 
5 1 
32 
6. 
20S 
82 
39 
Five weeks 
i. 
167 
164 
98 
0 0 
■j 
O 
2 
2. 
76 
*7 0 
/ 3 
97 
1 0 
4 
1 
3 - 
*45 
I42 
98 
1 1 
6 
2 
4 - 
152 
150 
98 
2 0 
6 
• 2 
£g 
6 . 
68 
64 
94 
1 1 
3 
2 
218 
212 
98 
0 0 
0 
0 
Eight weeks 
i. 
1S0 
r 5 5 
86 
3 0 
19 
13 
2. 
216 
189 
88 
7 
3 
2 
3 - 
105 
90 
Sc; 
5 1 
hr 
/ 
4 
Six weeks 
I. 
305 
159 
52 
5 
n 
2 
2. 
12 c; 
47 
it 
2 0 
26 
6 
3 * 
207 
x 54 
54 
4 - 
279 
x 45 
52 
6 2 
10 
0 
5 - 
MT 
74 
5 ° 
It will be seen from Section A of Table I that there are enormous 
numbers of bacteria present on the external surfaces of the galls, and of 
these bacteria a large percentage is always B. tumefaciens. Section B of 
Table I shows that it is possible to remove most of the organisms by 
washing, though B. tumefaciens as well as other bacteria remain in small 
numbers. Section C of the table shows the small increase in the total 
bacteria found when the galls are cut into pieces, but there appears no 
justification from the figures to assume that B. tumefaciens is present in 
greater proportions than on the exterior of the unwashed gall. The num- 
