[339] SCIENTIFIC MANUAL. 53 



pistils. The sepals, all taken together, form the calyx; 

 the petals, collectively, form the carolla. 



The Circulation of Sap will 

 now be considered only so 

 far as a knowledge of it may 

 be thought useful to the far 

 mer. 



All of the functions of 

 vegetable nutrition may be 

 expressed in three words, 

 viz : imbibition, assimilation Figure 14. 



Section of cherry blossom, showing every 

 and growth. part of the flower, 



Imbibition takes place through the root-hairs, the leaves 

 and green parts of the bark, principally by osmose, but to 

 some extent by capillary attraction, and is confined to 

 liquids and gases, the former beiny derived chiefly from 

 the soil, the latter principally from the air. All of the 

 ash element (that which remains when vegetable matter is 

 burned in the air,) of plants is imbibed in solution in 

 water by the -roots, as well as some of the organic ele- 

 ments which pass off into the air when the plant is burned. 

 The importance of this root action will be appreciated 

 when it is remembered that plants, in the fresh state, con- 

 tain from 70 to 90 per cent, of water. 



The following tables, taken from Johnson's "How Crops 

 Grow," show the percentages of water in some common 

 agricultural products, fresh and air-dried. These percent- 

 ages vary in different plants of the same species, and in 

 the different parts of the same plant. The amount varies 

 also at different stages of growth, with the amount of 

 moisture in the soil in which it grows, and the humidity 

 of the air by which it is surrounded. 



