HOW THE PLANT LIVES 123 



directly towards that slit, and even through it 

 to the brighter light. 



211. Plants are sensitive to gravitation. The 

 first root of the germinating seed is so sensitive 

 to gravity that it ordinarily grows downward, 

 wherever it may be and whatever may be its 

 position. On the other hand, the first shoot is 

 oppositely affected by gravity, and if a potted 

 seedling is placed horizontally the stem soon 

 directs itself upward: While its general tend- 

 ency is downward, the root is nevertheless 

 attracted in any direction by the presence of 

 water. 



212. The reactions of plants to their environ- 

 ments or surroundings may cause the plants to 

 vary, or to assume new forms or characteristics; 

 and these new features may be of use to the 

 farmer. Thus, with more light, the better are 

 the roses or carnations grown under glass; the 

 richer the soil, the stronger is the growth ; the 

 higher the altitude or latitude, the greater is the 

 proportion of dwarf plants. 



SUGGESTIONS O.V CHAPTER VIII 



182o. A salt is the substance formed from the union of an acid 

 with some inorganic substance or base. The salt may be neutral, 

 neither acid nor alkaline. Thus sulfuric acid and lime form 

 the salt, sulfate of lime or gypsum; nitric acid and caustic soda 

 form the salt nitrate of soda; muriatic (hydrochloric) acid and 



