211 



Having secured the production of a bright, 

 hard, glassy stem, the next desideratum is to 

 develop a long, well-filled ear. Towards this end, 

 available ammonia or nitrogen, phosphorus, potash, 

 and magnesia are indispensable. Ammonia 

 (spirits of hartshorn) is necessary to the forma- 

 tion of the combustible part of the seed, while 

 the other ingredients mentioned are required to 

 assist in the formation of the incombustible part . 

 In 100 parts of wheat-ash there are the following 

 substances, viz. 



Silica..... 2'28 



Phosphoric Acid 45-73 



Sulphuric Acid 0-32 



Lime >..... 2 OG 



Magnesia 10-94 



Peroxide of Iron 2'04 



Potash 32*24 



Soda 4'OG 



Chloride of Sodium , 0'27 



Total 99-94 



The quantity of ash in wheat varies from 1 to 

 2^ per cent., the average being about 1*69. The 

 amount of phosphoric acid in any given quantity 

 of wheat- ash varies from 40 to 50 per cent. 

 Seeds having a thick cuticle or bran, and little 

 gluten, contain a smaller percentage of phosphoric 

 acid, and more silica. About one-third of the 

 ash is potash ; in nearly all cases, magnesia varies 

 from 9 to 14 per cent., lime from 1^ to 6 per cent. 

 Peroxide of iron is seldom as abundant as in the 



