1907] DOUGLAS—INTUMESCENCES ON POTATO 239 
the greenhouse, to be used for the purpose of experiment. Eighteen 
of the potatoes were planted whole, while in the other pots were 
placed pieces containing two or three eyes. All of the potatoes were 
of good size and healthy. By April 4 several shoots had come up 
some distance from the ground and were covered with the bell jars. 
EXPERIMENT I 
Four pots of young plants with a few rather small young leaves 
were placed under bell jars in a well-lighted position in the green- 
house. The temperature of the air within the jars at the time of the 
setting-up of the experiment was 88° F. For three or four days after 
it was damp and cold, with only intermittent periods of sunshine. 
The temperature within the jars averaged about 65°F. In five to 
six days, after the temperature had increased to 68° F., intumescences 
began to appear. 
Pot 1. Three shoots (from a cut potato), 205,172,128™™ high respectively; 
all had rather small leaves. 
ot 2. Two shoots (from a cut potato), both 62™™ high, with young leaves. 
Pot 3. One shoot (from a whole potato), 36™™ high, with young leaves. 
Pot 4. Two shoots (from a whole potato), 32 and 61™™ high, with small 
leaves. 
Results 
No. 1. After six days intumescences began to appear on all three plants and 
to assume the characteristic appearance. They were scattered over most of the 
leaves of the plant and were very numerous on two or three of them. Four days 
later they had become dry and blackened, but in two days more new ones had 
appeared. 
No. 2. In five days intumescences had appeared on both shoots, although 
they were rather few and scattered over various leaves. 
No. 3. In five days intumescences had formed, but not profusely. 
No. 4. In five days a few intumescences had formed. 
Intumescences were thus formed upon all of the shoots, but were 
more numerous on the shoots of pot 1. This was probably due to the 
fact that these plants were farther developed than the others and 
consequently did not grow so fast. The other plants were very 
young and grew rapidly, and in consequence made use of more water 
in growth than the other shoots. A discussion of the connection 
between growth and the formation of intumescences will be taken up 
later in this paper. 
