Studies of Heaeth in Potatoes. 
21 
Every warm summer, in the corn belt, potato leaves roll as 
they did in the epidemic of leaf-roll in Colorado, but they usually 
recover to a large extent, with good fall weather. For many years, 
in the Greelev district, if leaves were once rolled bv long continued 
heat and heavy soil and heat, or watering in hot weather, all chances 
for a real good crop were considered to be past. There is a strong 
probability that it is the fungus factor that makes the leaf-roll 
condition permanent. Tt seems to be the sum of poor nutrition, a 
starvation matter, due to root injury. 
The Influence of vSori. Heat and Warm Air. 
On April 8th, the plants in one cross row were transferred from 
each of the other cabinets to the 95° cabinet, and part of them were 
covered with a glass case, heated by two 32 c. p. carbon lamps to 
Figure 13.—A case in which summe^* air temperatures were produced by 
heating with large electric globes. The temperature of the air proved to be a 
comparatively unimportant factor of potato health. 
an average temperature of 90° (ranging from 75° at night to 
110° in the sun) and well ventilated, tO' simulate summer heated air. 
We give the detailed records with the cuts and in the table. (See 
Fig-nre 13.) 
Those plants which had been wet and warm were almost 
instantly wilted by transferance to the 95° cabinet. Those that 
had been dry or cool stood up much longer. The addition of 
heated air in the glass case made very little difference to the plant 
troubles or in the time of going down from the soil heat. 
