THE LEAF AND ITS FUNCTIONS 85 



304. Wh}^ does a sliortage of water stunt a plant? 



305. Is transpiration ai)t to be liif^h or low when growth is most rapid? 

 Explain. 



306. Plants generallj^ grow faster at night than in the daytime. 

 Why? 



307. How do you reconcile the fact that plants grow faster at night 

 than in the daytime, with the fact that light is necessary for the manu- 

 facture of food? 



308. Plants generally grow faster in wet weather than in dry. Why? 



309. Why do plants often suffer from "scalding" after a brief summer 

 shower in the middle of the day? 



310. Can you think of any other reason than the presence of shade 

 which may tend to make a forest cool? 



311. The planting of rank-growing species like the sunflower has 

 sometimes been thought to reduce the amount of malaria in malarial 

 districts. What basis in fact is there for this belief? 



312. Name one way in which the presence of a forest tends to increase 

 the loss of water from the soil and one way in which it tends to decrease 

 it. Do you think that a soil will lose water faster if it is covered with 

 forest or if it is not? Explain. 



313. Why is the effect of a killing frost in the fall usually not evident 

 on the following morning until the sun has been up for some time? 



314. If a plant has been "touched" by the fi'ost but not killed, whj' 

 is it sometimes possible to restore it by sprinkling it with water and 

 placing it in a cool, shaded place? 



315. What structural modifications do .you know of in plants which 

 tend to result in checking transpiration? 



316. What characteristics must drought-resistant plants possess? 



317. The leaves of corn and other grasses often roll or curl when it is 

 very hot or dry. Why is this and of what advantage may it be to the 

 plant? 



318. The leaves of desert plants are usually leather)', fleshy of very 

 small, l^kplain. 



319. The leaves of Eucalyptus, a tree which floui'ishes in warm, dry 

 regions, hang vertically on the branches. Explain how this is of 

 advantage to the plant. 



