304 THE LEAVES OF PLANTS. 



which has been vitiated. Thus Providence provides a living 

 check upon malaria, and has admirably ordained that one of 

 the kingdoms of nature should render and maintain the world 

 in such a state as to be habitable by the other. 



ESTHER. 



Leaves perform important functions to plants. 

 MRS. F. 



Yes; they are at once the organs of respiration, digestion, 

 and nutrition. 



HENRIETTA. 



Then why do gardeners so often take them off the fruit 

 trees? 



MRS. F. 



From the greatest ignorance. If a branch be stripped of 

 its leaves for a whole summer, it will either die or not increase 

 in size perceptibly. Deprive a tree of its leaves, and the 

 flowers lose their color; and if it be before the fruit has com- 

 menced ripening, the fruit will fall off and not ripen; or if in 

 a more advanced stage, it will diminish its flavor considera- 

 bly. This, therefore, is one of the numerous examples of the 

 benefit which is daily accruing to horticulture from the know- 

 ledge of vegetable physiology. 



ESTHER. 

 Do plants grow most by night, or by day? 



MRS. F. 



They grow chiefly by day, as appears from the few observa- 

 tions which have been made upon the subject. Wheat and barley 

 were found to grow by day nearly twice as fast as by night; 

 but the diurnal changes of day and night are as necessary to the 

 well-being of plants as they are to that of animated beings. 

 If plants were kept incessantly growing in light, they would 

 be perpetually decomposing carbonic acid, and would in con- 

 sequence, become so stunted that there could be no such thing 



