The Utilization of Foods 



89 



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Fig. 53. A tobacco field in Connecticut. The plants are grown for their leaves. 



the grass leaf is at the base. A more exact determination of 

 the growing region may be made by marking a young grass 

 leaf into equal spaces with India ink. This will show that as 

 the leaf develops, it is continually pushed upward and outward 

 from the node where it is attached. This mode of growth is 

 characteristic not only of grasses but of many other plants 

 having parallel- veined leaves. 



Net-veined leaves. The net-veined leaves develop differ- 

 ently from the leaves of either ferns or grasses. An exami- 

 nation of a growing net- veined leaf will show that all parts are 

 equally firm. The best method of study is to mark the young 

 leaf into equal squares by means of two series of parallel lines 

 at right angles to each other. A geranium or nasturtium leaf 

 serves well for this purpose. After several days it will be 

 seen that the only change has been an increase in size of the 



