Il8 BOTANY or CROP PLANTS 



in a fertile soil. The application of fertilizers may increase 

 the total amount of water taken in by the plant, due to 

 increased plant growth, but the requirement per unit of 

 dry matter is lowered. 



The effect of cUmate and soil on the composition of the 

 grain has been discussed. 



Uses of Wheat. — By far the largest proportion of the 

 world's supply of flour is made from wheat. As already 

 stated, the hard wheats, particularly durum varieties, are 

 used extensively in the manufacture of macaroni and alHed 

 products. In the manufacture of macaroni, the wheat is 

 first ground into a course product known as "semolina.''^ 



Fig. 42. — Diagram showing the percentage of the world's wheat crop pro- 

 duced by the different countries in 1915. 



It is freed then of any adhering particles of fine flour and 

 bran. The semolina is mixed with about 30 per cent, of 

 water, worked into a stiff dough, and given a thorough 

 kneeding. The dough is then forced through a press, from 

 which it issues in long hollow tubes. These tubes of moist 

 dough are then carefully dried in a manner to prevent them 

 from becoming too brittle or sour. Vermicelli and spaghetti 



