THE ROTATION OF CROPS. 171 



in respect to forest-trees, nature, in many cases, clearly indicates 

 the necessity of a change of production, in that where you cut 

 down a forest of oak, it is usually followed by a growth of pine, 

 and where you remove a forest of pine, there will spring up a 

 growth of oak ; the soft and the hard woods thus alternating with 

 each other. 



Sometimes it is found that the substitution of a single differ 

 ent crop is sufficient to prepare the land for the repetition of the 

 former one. In some cases, the crop can be repeated with ad 

 vantage after an interval of two, three, or more years. In some 

 instances, the land, if left to itself, or what is called a naked 

 fallow, becomes, after a year or more, prepared for the repetition 

 of the first crop. The regular and plentiful manuring of the 

 land will enable the land to bear the repetition, though there 

 are cases in which even this ceases to restore the land to its 

 former condition. It is found likewise that crops of the same 

 family, though not of the same kind, will not follow each other 

 to advantage. Thus the cereal grains, wheat, rye, barley, and 

 oats, are considered improper to follow each other in immediate 

 succession. The English divide their crops into two kinds, white 

 and green crops. The grain crops are white crops ; the green 

 crops are the esculent vegetables, such as turnips, ruta-baga or 

 swedes, carrots, parsnips, beets, cabbages, peas, beans ; although 

 the two latter, which are cultivated for their seeds, would seem 

 more properly placed among the white crops. There is, how 

 ever, another distinction between the narrow-leaved and the 

 broad-leaved plants, which is to be considered in this case. The 

 narrow-leaved plants, such as the grains and grasses, receive 

 their nourishment mainly, as is supposed, from their roots, which 

 are numerous and fibrous ; the broad-leaved plants, such as tur 

 nips, cabbages, beans, and peas, and the clovers, receive their 

 nourishment chiefly from the atmosphere, and do not therefore 

 so severely tax the soil. This difference, it is supposed, allows 

 of one of these crops being alternated with the other without 

 prejudice to either. I am giving, in this case, the theory of 

 others, which certainly, to a casual observer, seems plausible 

 enough. I trust I may be allowed to demur to it, or at least to 

 hold my judgment in suspense, because, to my mind, the proof 

 is wanting. It remains, in my opinion, yet to be established 

 that any plants receive their nourishment through their leaves. 



