4 Department Circular 376, U. S. Dept. of Agriculture 
Fic. 3.—Typical trees classified as possessing large galls, one (left) showing the 
woolly-knot type and the other a simple form of crown gall 
Fig. 4.—One of the type of trees classified as 
doubtful 
In the experiments of 1925 
the organic-mercury treat- 
ment was given to 2,619 
grafts, representing a num- 
ber of different varieties, 
with the result that the total 
number of trees obtained at 
digging time with both large 
and small galls amounted to 
6.1+per cent, as compared 
with 32.6 per cent on 2,619 
untreated grafts of the same 
varieties which were used as 
checks. The proportion of 
the total number of large 
galls in the treated grafts of 
all varieties was 2 per cent 
and in the untreated or 
check grafts 28.7 per cent, as 
shown in Table 1. 
Figure 5 represents a typi- 
cal lot of trees resulting 
from the use of the organic- 
mercury compound. ‘This 
lot was selected because it 
illustrates about the average 
control obtained in the ex- 
periments in 1925, whereas 
Figure 6 shows the corre- 
