THE LIFE OF A PLANT 



271 



elements of which starch and sugar are composed carbon, 

 oxygen, and hydrogen to form proteid, another plant food. 

 Starch making can occur only in green leaves and only in the 

 light, but proteid making can take place in other parts of the 

 plant, and in darkness as well as in light. 



FIG. 143. ASA GRAY: BOTANIST. 1810-1888 



Very few great investigators are willing to take the trouble to prepare 

 textbooks of their subject, much less elementary textbooks. But Gray was 

 also a great educator and his ambition was to develop the science of botany 

 by training the greatest possible number, from the elementary schools to the 

 university. . . . For nearly half a century he taught not only the teachers 

 but also the children. JOHN M. COULTER, in Leading American Men of 

 Science. 



305. The Importance of the Chemical Work of Plants. 

 Plants themselves use these manufactured foods to build up 

 their tissues to grow, as we say. If there were an inex- 

 haustible supply of carbon dioxide in the air and of minerals 

 in the soil, plants could get along without animals. But ani- 



