go 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. 
WOOO 2500000 
Fic. 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 
