STATING THE CASE. 31 



attract insects. Those desirous of seeing how the 

 leaves of plants owe their shapes to their ability to 

 obtain carbonic acid in their natural habitats, should 

 read Grant Allen's charming work on The Shapes of 

 Leaves. 



The leaves of plants have received their charac- 

 teristic shapes and positions under circumstances 

 where chance and not laiv seems to the thoughtless 

 mind the most probable agent. The leaves are 

 fixed, and cannot go in search of the carbon atoms. 

 The wind, however, brings the latter to them, and 

 every gentle breeze, as it stirs the leaves with cha- 

 racteristic rustle, is laden with fresh supplies. The 

 breezes which sweep the crowded streets and close 

 alleys of our large cities and towns carry off the 

 carbonic acid, away perhaps to the primeval forests 

 of the great Amazons valley, or to the pine -clad 

 slopes of the Alps. Our own grassy hillsides and 

 meadows partake of the supply. Everywhere the 

 oxygen of the carbonic acid is returned to the 

 atmosphere again, to invigorate and regulate the 

 bodies of animals and men. Nearly twenty -five 

 millions of square miles of leaf surfaces are engaged 

 on the dry-land surface of our globe in removing the 

 carbonic acid daily thrown into the atmosphere ! 



The " raw material " of plants — that made up of 

 the salts, etc., extracted by the roots from the soil, 

 and by the leaves from the air — is Protoplasm. It is 

 a living, usually a jelly-like, substance, composed of 



