288 



On the Rotation of Crops» 



two plots showed remarkable health, though the plants of each 

 assumed a very different mode of growth. On the one (No. 1), 

 every shrub was sturdy^ but not talb and its foliage beautifully 

 verdant. In the other (No. 2), the canes grew to the height of 

 eight feet^ or more ; the surface soil of the garden was shallow, 

 resting on a bed of chalk. These plants gave in and hardly 

 a cane three feet high was left in the following year. 



The stout plants of the other garden — the soil of which ap- 

 peared to be a hazel loam over shaly stones—continued to flourish, 

 and bore excellent fruit. My plants deteriorated gradually, 

 though the soil was deep, and every effort was made to keep it in 

 heart. I ascertained that the stout plants of the garden No. 1 

 were never permitted to occupy the same site during a longer 

 period than five years ; and that nevf beds were formed in regular 

 succession by planting strong suckers in parts of the garden 

 remote from the bearing beds, which, at the termination of the 

 assigned period, were grubbed, cleared of roots, and put under 

 some vegetable crop. 



Comparing these facts, I arrived at the inference which I stated 

 in the following terms : — Particular plants convey into the soil, 

 through the channels of their reducent vessels, certain specific 

 fluids, which, in process of time, saturate it, and thus render it 

 incapable of furnishing those plants any longer with wholesome 

 aliment : in fact, the soil becomes replete with fecal and excre- 

 mentitious matter, and on such the individual plant which has 

 yielded it cannot feed ; but it is not exhausted ; so far from that, 

 it is, to all intents and purposes, manured for a crop of a different 

 nature : and thus, by the theory of interchange between the fluids 

 of the plant and those of the soil, we are enabled, philosophically, 

 to account for the benefit which is derived from a change of 

 crops." — (Domestic Gardener's Manual, 1830, p. 397.) 



Wholly ignorant at that period of the hypothesis of De Can- 

 dolle, or that this philosopher had penned one word on the sub- 

 ject, I arrived, it should appear, at a corresponding deduction 

 from facts. Subsequent observation has afforded proofs corro- 

 borative of the theory, while it has presented the means to inter- 

 pret the doctrine by reference solely to natural agents and the 

 vegetable vital principle. 



1st. If we investigate the soil wherein a rank crop of any kind 

 has grown, we shall rarely fail to detect the presence of a more or 

 less powerful specific odour : this is traceable upon turning over 

 the surface of a cabbage or broccoli bed, or that in the vicinity of 

 a row of peas, beans, or kidney-beans; all the hrassicas, and 

 many leguminosce (that is, of the cabbage, and many of the bean 

 tribe) afford clear evidence of this fact; and the only inference 

 that can be drawn from it is, that the ground is imbued with 



