ANALYSIS OF SOILS. 49 



Fortunately, a remedy cheaper, more accessible, 

 and less difficult, is found in that great diversity of 

 habits and character which mark the vegetable" 

 races. We shall, therefore, in what remains of this 

 chapter, indicate the principal of these, as furnish 

 ing the basis of all rational agriculture. 



1st. Plants have different systems of roots, stems, 

 and leaves, and adopt themselves, accordingly, to dif- 

 ferent kinds of soils : the tussilago prefer clay, the 

 spergula sand ; asparagus will not flourish on a bed 

 of granite, nor muscus Islandicus on one of allu- 

 vion. It is obvious that fibrous-rooted plants, which 

 occupy only the surface of the earth, can subsist on 

 comparatively stiff and compact soils, in which 

 those of the leguminous and cruciform families 

 would perish, from inability to penetrate and divide. 



2d. Plants of the same or of a similar kind do not 

 follow each other advantageously in the same soil. 

 Every careful observer must have seen how grasses 

 alternate in meadows or pastures where nature is 

 left to herself. At one time timothy, at another 

 clover, at a third redtop, and at a fourth blue grass 

 prevails. The same remark applies to forest trees ; 

 the original growth of wood is rarely succeeded by 

 a second of the same kind ; pine is followed by 

 oak, oak by chestnut, chestnut by hickory. A young 

 apple-tree will not live in the place where an old 

 one has died ; even the pear-tree does not thrive in 

 succession to an apple ? tree, but stone fruit will 

 follow either with advantage. " In the Gautinois," 

 says Bosc, " saffron is not resumed but after a lapse 

 of twenty years; and in the Netherlands, flax and 

 colzat require an interval of six years. Pease, when 

 they follow beans, give a lighter crop than when 

 they succeed plants of another family."* 



* The ill effect of a succession of crops of the same kind was 

 not unknown to the Romans. We have proof of this in the fol- 

 lowing passage of Festus : " Restibilis ager fit qui continuo 



