266 LEAVES 
transpiration, the plant is notin danger. But itis not uncommon 
to see Corn with leaves rolled and Potatoes, Cotton, Clover, and 
other plants wilted during dry hot days. These plants are losing 
water faster than it can be replaced from the roots. These 
plants are in danger because their living cells are becoming dry, 
and too much drying results in death. More plants die on 
account of transpiration than anything else. 
The important thing for the plant is the maintenance of a 
proper balance between supply and loss of water. The plant can 
endure rapid transpiration, if a copious supply of water is coming 
up from the roots; but, if the ground is dry about the roots, the 
root system small, or water hard to obtain from the soil, as is the 
; is 
BAAD AAABOSBOAAGH 
Fic. 238. — A portion of a cross orn ituei roe 
section through a node of Sugar Fic. 239.— A portion of a sec- 
Canc, showing rods of wax secreted tion through a Mullein leaf, show- 
by the epidermis. Enlarged many ing the epidermis with its branched 
times. After De Bary. hairs. After Andrews. 
case in soils that are cold or frozen, then even a small amount of 
transpiration may be injurious. 
Protection against Injuries Resulting from Transpiration. — 
Plants may be protected against the injurious effects of trans- 
piration by having their transpiring surface modified, or by 
having the soil moisture increased or conserved. 
There are various ways in which plants modify their transpiring 
surface. Some plants, such as the Carnation, Pine, and many 
plants of the desert, have the epidermis of their leaves covered 
with a heavy layer of cutin. Sometimes, as in Cabbage, Sugar 
Cane, and Wheat, the epidermis is covered with a waxy bloom. 
(Fig. 238.) Many plants are protected by a covering of hairs. 
(Fig. 289.) Some plants, such as the Cacti of the desert, have 
reduced their leaves to mere spines which offer only little trans- 
