62 HOW CROPS GROW. 



AMOUNT OF CELLULOSE IN PLANTS. 



Per cent. Per cent. 



Potato tuber 1.1 Red clover plant in flower. . .10 



Wheat kernel 3.0 " " hay 34 



Wheat meal 0.7 Timothy " 23 



Maize kernel 5.5 Maize cobs 38 



Barley " ... 8.0 Oat straw 40 



Oat " 10.3 Wheat" 48 



Buckwheat kernel 15.0 Rye " 54 



Starch, C 12 H 20 O 10 . The cells of the seeds of wheat, 

 corn, and all other grains, and the tubers of the potato, 

 contain this familiar body in great abundance. It occurs 

 also in the wood of all forest trees, especially in autumn 

 and winter. It accumulates in extraordinary quantity in 

 the pith of some plants, as in the Sago-palm, (Metroxylon 

 jRumphii,) of the Malay Islands, a single tree of which 

 may yield 800 Ibs. 



Starch occurs in greater or less quantity in every plant 

 that has been examined for it. 



The preparation of starch from the potato is very sim- 

 ple. The potato contains, on the average, 76 per cent wa- 

 ter, 20 per cent starch, and 1 per cent of cellulose, while 

 the remaining 3 per cent consists mostly of matters which 

 are easily soluble in water. By grating, the potatoes are 

 reduced to a pulp ; the cells are thus broken and the starch- 

 grains set at liberty. The pulp is then agitated on a fine 

 sieve, in a stream of water. The washings run off milky, 

 from suspended starch, while the cellulose is retained by 

 the sieve. The milky fluid is allowed to rest in vats until 

 the starch is deposited. It is then poured off, and the 

 starch is collected and dried. 



Wheat-starch is commonly made by allowing wheaten 

 flour mixed with water to ferment for several weeks. By 

 this process the gluten, etc., are converted into soluble 

 matters, which are removed by washing, from the unalter- 

 ed starch. 



Starch is now largely manufactured from maize. A 



