120 ELEMElSTTAllY AGBICULTURAL CHEMISTRY 



3. Miscellaneous seeds — buckwheat, cotton-seed, linseed, 



hemp-seed, rape-seed, castor beans, sunflower-seed, &c. 



4. Fruits — apples, pears, plums, apricots, peachej\ 



oranges, melons, pumpkins, bananas, grapes. 



1. The Cereals. — The seeds of these plants are character- 

 ised by their richness in starch. Their straw generally con- 

 tains a large amount of silica, which, however, does not appear 

 to be essential to the plant. The silica is probably absorbed 

 in the form of soluble silicates — e.g., of potassium, the metal 

 being used by the plant and the silica deposited, chiefly in the 

 stem, as an excretion. 



Another characteristic of cereals is their richness in phos- 

 phoric acid and comparative poverty in lime. This is most 

 marked in the grain itself, but is also shared by the straw. 



Wheat {Triticum vulgar e) in temperate climates is usually 

 autumn-sown, and therefore has a longer period of growth 

 than barley or oats. It is consequently better able to supply 

 itself with the necessary food from the soil. The land, how- 

 ever, loses the spring tillage, which, by aerating the soil, is 

 conducive to nitrification, and nitrogenous manures are there- 

 fore more often required by wheat than by other common 

 cereals. 



Wheat straw, when ripe, is remarkable for the large amount 

 of silica and the small proportion of nutritive matter which it 

 contains. 



The wheat grain is particularly suited for the manufacture 

 of bread because of its large content (8 to 10 per cent.) of 

 gluten, and the richness of this gluten in the peculiarly sticky 

 gliadin. This enables wheat flour to furnish a light, porous, 

 ipongy, and palatable bread when the dough is inflated by 

 carbonic acid, as in baking. In warm climates, especially 

 when much rainy weather occurs in the summer, wheat (also 

 barley and oats) becomes very liable to the attacks of fun- 

 gous diseases — e.g., rust — and is in consequence only grown 

 for its seed during the dry season, and usually by the aid of 



