ROOT CROPS. 133 



exported from this country to England, for the use of 

 British farmers, who know its value and are eager to 

 purchase it. 



SECTION III. OF THE ROOT CROPS 



In the root crops we fii?** quite different character- 

 istics from any yet mentioned. In some of them 

 starch almost entirely disappears, other bodies of a 

 somewhat similar nature taking its place. The po- 

 tato, and a few other less known crops, are exceptions. 

 Another distinguishing feature is the quantity of water 

 which they all contain. About 16 per cent has been 

 the highest amount hitherto mentioned, but now we 

 shall find a very greatly increased proportion. 



The potato, as taken from the ground, contains 

 about 75 per cent of water, or three fourths of its 

 whole weight; of the remainder, from 14 to 20 per 

 cent is starch. There is about 1 per ceat of a nitro- 

 genous compound like albumen, and the rest is made 

 up of woody fibre, gum, and sugar. The starch of the 

 potato is contained in little cells, and is in small rounded 

 masses. Grating destroys the cells, and water will 

 separate the starch as described before. When the 

 tuber is attacked by potato disease, its first appear- 

 ance is in the walls of the cells, the starch remaining 

 uninjured for a considerable time; it can even be sepa- 

 rated after the disease has progressed till the potato is 

 worthless for any other purpose. 



By keeping, the starch of potatoes gradually dimi- 

 nishes, being converted into a species of gum. This 

 is the reason why potatoes are apt to be watery and 

 soft in the spring, and to have a disagreeable sweet- 

 ish taste. When they are allowed to sprout, from 

 being in too warm a place, a great deterioration en- 

 sues. This is for the reason that the starch, as in the 

 grains, being turned in a great degree to sugar an^ 

 12 



