1907] DOUGLAS—INTUMESCENCES ON POTATO 241 
EXPERIMENT III 
The next question which arose was in regard to the effect of 
increasing the absorption of water by the roots. Pots were placed 
over the warm water pipes, keeping the soil at a temperature of 70° F. 
The position of the plant was under whitewashed glass in the green- 
house. 
Pot 11. One shoot (from a whole potato), 60™™ high, with many large leaves. 
Pot 12. Two shoots (from a whole potato), 65 and 60™™ high, with many large 
leaves, 
Results 
No. 11. After four days many intumescences were produced on many leaves. 
No. 12. After four days intumescences formed on nearly all the leaves and 
were very numerous on some of them. These intumescences continued to appear 
for several days. 
EXPERIMENT IV 
Two plants were kept under the same conditions as in the pre- 
ceding experiment, with the exception of being darkened by covering 
their bell jars with black cloth. 
Pot 13. Two shoots (from a whole potato), 102 and 62™™ high, with small 
leaves. 
Pot 14. Two shoots (from a whole potato), 185 and 130™™ high, with large 
leaves. 
No intumescences were formed after ten days on either plant; the growth, 
however, in both cases was very rapid. 
EXPERIMENT V 
The absorption of water was lessened by keeping the roots cold. 
Ice was kept packed around the pots, making an average temperature 
of the soil about 58°F. The pots were cut off from the air above 
in the bell jar by a thick blotting-paper covering. The air in the bell 
jars was kept warm by the sun (about 78° F.) during the days while 
the experiment was going on. A saturated atmosphere was produced 
within the jars by the evaporation from dishes of water. 
In light 
Pot. 15. Two shoots (from a cut potato), 120 and 105™™ high, with large 
leaves. 
Pot 16. One shoot (from a cut potato), 190™™ high, with large leaves. 
