90 Field, Forest, and Wayside Flowers 



another in shape and size, and they are laid to- 

 gether loosely, like the boulders in those gray 

 walls which separate New England pastures. 



In this lower leaf-tissue there are generally a 

 number of irregular cavities or air-spaces. 



Each separate leaf-cell is a little bag of delicate, 

 transparent skin, filled with colorless jelly. 



FIG. 16. Magnified section of the green tissue of a leaf. 



(From the Vegetable World.) 



This jelly is protoplasm, which Huxley has 

 called "the physical basis of life." The living 

 creature, animal or plant, is largely built of it. 

 Science teaches that its chemical composition is 

 closely akin to that of the white of an egg, and 

 that its elements are oxygen, hydrogen, carbon, 

 nitrogen, phosphorus, and sulphur. 



But the proportions of these ingredients vary 

 almost from moment to moment, and with them 



