(2) 
section, indicate thé principal of these, as furnishing 
the basis of all rational agriculture. 
ist, Plants have different systems of roots, stems and 
leaves, and adapt themselves accordingly to different 
kinds of soils : the Tussilago prefers clay, the Sper- 
gula sand; Asparagus will not flourish on a bed of 
granit, nor Muscus Islandicus on one of alluvion.— 
It is obvious, that fibrous rooted plants, which occu- 
py only the surface of the earth, can subsist on com- 
paratively stiffand compact soils, in which those of 
the leguminous and cruciform families would per- 
ish, from inability to penetrate and divide. 
2d. Plants of the same or of a similar kind, do not 
follow each other advantageously in the some 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 red-top, and at a fourth blue grass 
prevails. The same remark applies to forest trees ; 
ihe original growth of wood is rarely succeeded by 
a second of thesame kind; pine is followed by 
oak, oak by chesnut, chesnut 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 fol- 
low 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. Peas, when 
they follow beans, give a lighter crop than when 
they succeed plants of another family.”(1) 
(1) The ill effect of a succession of crops of the same kind was not unknown to the 
