114 
N. C. AGRICULTURAL EXPERIMENT STATION. 
TABLE VII.—SHOWING TOXICITY OF COPPER SULPHATE. 
o = Not viable; 4 = Viable. 
Time in Hours. 
c ° . 
CtfCO £ 
— 
-— 
— 
TO O +3 
~12 
X 
X 
X 
5 
1 2 
X 
7 
12 
% 
X 
X 
11 
12 
l 
It? 
IX 
IX 
IX 
llT 
IX 
^12 
m 
IX 
4 
8 
24 
n 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
O- 
o 
o 
o 
o 
o 
o 
o 
100 
n 
+ 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
O 
o 
o 
o 
o 
o 
o 
o 
200 
# 
n 
— 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
o 
o 
o 
400 
n 
— 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
o 
o 
o 
800 
n 
— 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
1600 
n 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
3200 
n 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
4 
6400 
In all cases here copper sulphate failed to cause death of the my- 
•celium, until the mycelium had been subjected to the solution for 80 
minutes. It then caused death with the two stronger solutions, N"/100 
and 1NT/200. X/400 and H/800 did not cause death till the expira¬ 
tion of 105 minutes, and even 24 hours soaking in the three weaker 
solutions, JNT/1600, JNT/3200 and JNT/6400, failed to kill the fungus. 
In conditions unfavorable to mycelial growth, for example upon 
plain agar, or agar otherwise deficient in nutrients the gonidia were 
produced in abundance. Their production also occurred in the midst 
of dense masses of mycelium in late periods, apparently due to the 
unfavorable effects of lack of nutrients or to the development of in¬ 
hibiting products. They were also formed abundantly from the germ 
tubes of ascospores in drop cultures in sterile water within a few 
days after the cultures were made. Here no nutriment was accessible 
except that present in the spore itself. 
Careful count was made of the number of sclerotia upon various 
parts of affected lettuce plants. The results are given in Table IX. 
These plants were naturally infected in the lettuce beds. It is 
seen that the greater number of sclerotia was formed in the axils of 
the leaves around the stem. Those formed in the ground on the root 
were produced only after the root had begun to decay. Xo plants 
that were examined, in which the roots had not begun to decay, 
showed signs of sclerotia below ground and in very few instances was 
there any external sign of the fungus in the parts below ground. 
If half of a bed of the usual size, 9 x 100 feet, hearing 2,000 plants, 
he diseased (this is not an uncommon percentage), it is seen that 
there may be formed as many as 17,100 sclerotia per bed. It is quite 
