THE LEAF AND ITS FUNCTIONS 83 



272. Which should j^ou keep mown more closely, a newly seeded lawn 

 or an old one? Why? 



273. Should lawn grass, when cut, be raked off the lawn or not? 

 Explain. 



274. Other things being equal, is it better to plant the rows of a 

 garden east and west, or north and south? Why? 



275. State two reasons why a garden planted near a shade tree is apt 

 to be unsatisfactory. 



276. Do you think that transpiration is essential for the life of the 

 plant? Explain. 



277. What process in animals may be said to correspond roughly 

 to the transpiration of plants? In what respects are the two processes 

 similar? 



278. From j'our knowledge of osmosis, explain wh}' it is that "the 

 amount of salts absorbed is practically independent of the amount of 

 water transpired by the plant". 



279. Just where in the leaf does evaporation take place during the 

 process of transpiration? 



280. What makes water leave the cytoplasm of the spongy layer cells 

 (or any others) and wet the cell walls? 



281. Why is it that the air in the air spaces of the spongy layer of the 

 leaf does not become so saturated with moisture that evaporation, and 

 consequently transpiration, will no longer take place? 



282. In general, the faster a plant loses water by transpiration, the 

 faster it will absorb it from the soil. Explain. 



283. Do you think that a plant would be able to thrive and grow 

 permanently in an atmosphere which is completely saturated with 

 moisture? Explain. 



284. Will transpiration be more rapid or less rapid if the sap of the 

 mcsophyll cells increases in concentration? 



285. Why does transpiration take place so much faster in wind than 

 in still air? 



286. Wliy do florists usually water the walls and walks of a green- 

 house as well as the plants themselves? 



287. Why does a plant wilt if its water supply fails? 



