SECTION V. 



Of the different Grasses, and other Plants, adapted for the Alter- 

 nate Husbandry. 



THE grasses, and other plants, best fitted for alternation, as green 

 crops with grain, are such as arrive at perfection in the shortest 

 space of time, or within the compass of two years ; such as have 

 their leaves broad and succulent, and that do not quickly run to 

 seed. Plants of this description are supposed to produce the 

 greatest weight of herbage at the least expense to the soil. 



It is a curious and well-known fact, that any species of plant 

 that has continued till its natural decay on a particular soil, can- 

 not be again immediately reared with equal success on the same 

 spot, till some other crop intervene ; but that a different species of 

 vegetable will there succeed better, for its peculiar period of life, 

 than it would on a soil naturally better adapted to its growth, 

 where it had just attained to perfect maturity. This holds good 

 with respect to annual plants as well as to those that continue to 

 live many years. But it is better seen in the former, as their habits 

 and duration in the soil are oftener and more directly within the 

 reach of common observation. 



On this antipathy of plants seems to depend the theory of alter- 

 nate cropping with green crops and grain varying in some mea- 

 sure according to the circumstances of soil and climate ; but the 

 principle appears to remain the same. 



On analysing a soil immediately before and after producing an 

 impoverishing crop, the results of such analysis do not point out 

 any diminution in the weight or proportions of its constituents 

 sufficient to account for the weight of vegetable matter produced. 

 The decomposing animal, and vegetable matters of the soil are the 

 only constituents wherein a sensible loss is perceived. 



M. Braconnot grew plants in substances free from any kind of 

 soil, as in flowers of sulphur, and in metal. He supplied the 

 plants with distilled water only. They arrived, by these means, 

 to a perfect state of maturity. The produce was submitted to 



