218 FOOD OF PLANTS. 



Class 3. Roots. 



"Water, per cent. 



Potatoes, ronnd pinkeyes 79-54 



" blue pinkeye, 73 '71 



" pinkeye 75 • 



" Scotch gray, 71 • 



Orange carrot, from 83 to 89 "52 



Blood beet, 86-42 



Turnips, 88- 



Mangel wurtzel, 85- 



It will be observed, on comparing the foregoing classes, that water is much greater in the 

 roots than grain. The state in which these classes are fed, is also worthy of note ; the grains 

 and grasses are fed dry, while the roots are fed green, they being so constituted as to retain 

 their water for a long time after they are removed from the earth ; while grains and grass be- 

 come dry and are fed in that condition. The amount retained in the grains and grasses does 

 not differ materially, and if the root should undergo a like depreciation, they would resemble 

 the herbage of plants ; tbe grasses when green lose on drying about 80 per cent of water. 

 Now, from the great amount of water which roots contain, and the small percentage of ash, 

 it has been maintained that they exhaust a soil less than the grains ; that the potato and turnip 

 may be grown without regarding very particularly the matter removed. In potash, however, 

 the exhaustion must be admitted to be excessive, when the great amount of substance re- 

 moved is taken into account. The nutritious matter of the root crops, which is derived ordi- 

 narily from an acre of ground, exceeds considerably that which is furnished by wheat, and 

 rather more than that which is produced by Indian corn. These facts seem to show that really 

 in the peculiar elements of roots their exhausting power exceeds that of wheat, "corn or beans. 

 These heavy root crops are usually fed to stock upon the farm, and hence there is no loss of 

 mineral matter. 



IMPORTANCE OF SUPPLYING PLANTS WITH PROPER FOOD. 



Plants are not confined absolutely to certain kinds of food ; their aliment may be varied, 

 and they will preserve, externally, their natural characteristics, provided this variation is not 

 excessive. It appears, from observation and experiment, that to a certain extent one element 

 of food may be substituted for another; soda and lime, for example, may take the place of 

 potash. It is not a matter of indifference whether tobacco and other plants contain lime or 

 potash. It may not be necessary to follow the natural affinities of the plant ; what we have 

 to do is to ascertain the effect of these aliments on their qualities or properties. If the salts 

 of lime predominate in tobacco its qualities arc injured. It matters not whether tobacco is a 

 potash or lime plant, in a state of nature, or has preference for lime rather than for potash ; it 

 is a fact merely, and by change from necessity, may afiFect the properties favorably. It is pro- 



