156 ALTERNATION OF CROPS. 



There is another distinguishing feature between the 

 culmiferous and leguminous classes we have named — the 

 form of their roots. The first are generally fibrous-rooted, 

 are more divided, spread themselves near the surface, 

 and draw their nourishment principally from the upper 

 stratum of the soil. The leguminous group are generally 

 spindle or tap-rooted, with few radicles, and consequently 

 draw most of their nourishment from the lower stratum 

 of the soil, and through the lower extremities of their 

 roots. Plants, says Chaptal, exhaust only that portion 

 of the soil which comes in contact with their roots ; and 

 a spindle root may be able to draw an abundance of nour- 

 ishment from land, the surface of which has been exhaust- 

 ed by short or creeping roots. The roots of plants of 

 the same or analogous species, continues the same writer, 

 always take a like direction, if situated in a soil which al- 

 lows them a free developement ; and thus they pass 

 through, and are supported by, the same layers of earth. 

 For this reason we seldom find trees prosper that take 

 the place of others of the same species, unless a suitable 

 period has been allowed for producing the decomposition 

 of the roots of the first, and thus supplying the earth with 

 fresh manure. 



Good husbandry, therefore, enjoins, that culmiferous 

 and leguminous crops should follow each other in suc- 

 cession, except where grass is made to intervene ; and it 

 matters little what crops are selected from the two classes. 

 The good judgement of the farmer may be here exercised 

 to determine which are likely to be to him the most ad- 

 vantageous. It may be proper to note two exceptions" 

 to this rule : Indian corn may, under certain contingen- 

 cies, be made to follow a small-grain crop to advantage, 

 and oats may be sometimes sown, as a fallow crop, upon 

 a grass ley ; as a fallow crop to precede wheat or rye, 

 and to supersede a naked fallow. Some soils, it is true, 

 are better suited to one kind of crop than another ; as, 

 for instance, calcareous clays, and strong loarns, are better 

 adapted to wheat than silicious gravels and sands ; while 

 the latter are better fitted to Indian corn, turnips, clover, 

 and other tap-rooted plants, than clays. And where In- 



