On the Rotation of Crops. 



287 



Mercunalis annua, &c., after washing their roots thoroughly, and 

 placing them in phials of pure water.* He obtained results which 

 proved indeed that the roots, so raised and washed, absorbed and 

 ejected certain chemical solutions ; but it must be admitted that a 

 plant of any species, when lifted from its earthy bed, is no longer 

 in its natural situation ; it becomes susceptil^le of the agency of 

 foreign substances, which Avould have been wholly inoperative had 

 it remained quiet and undisturbed. It has ever appeared to me 

 that pure chemistry cannot be legitimately employed to discover 

 or interpret the phenomena of the vital principle : its sphere of 

 action is the analysis of dead or effete matter, and the develop- 

 ment of its constituents ; for that which destroys life cannot inter- 

 pret the living functions : therefore, all experiments upon vegeta- 

 bles, by plunging their roots into solutions of lead, oxalate of 

 ammonia, and lime-water, though they lead to certain chemical 

 results, must be considered delusive, inasmuch as the exposed 

 and unprotected fibres are placed in media quite foreign to their 

 nature, and destructive ultimately of the vital principle. While 

 growing in soil, a plant is in its native element, protected and de- 

 fended ; it is in a medium wherein it can exert all its vital func- 

 tions. A young and tender balsam will live, and in a degree 

 thrive, though the mould of its pot be frequently watered to satu- 

 ration with a diluted solution of muriate of iron ; but, raise the 

 plant, and immerse its roots in that same solution, and it will pe- 

 rish in an hour ; though, previously, the soil have assumed the 

 appearance of rust of iron from the quantity of oxide which it has 

 separated from the water during the course of a fortnight. 



Thus it appears that no correct inference can be deduced from 

 any phenomena which are discoverable in plants, or portions of 

 plants, when they are acted upon by chemical agents, in situations 

 which are unfavourable to the due performance of the vital func- 

 tions. Under the im^pression of this fact, I was induced to 

 take that view of the theory of radical exudation which I made 

 public in the first edition of the ' Domestic Gardener's Manual;' 

 and which every subsequent observation has tended to confirm. 

 This I may now be permitted to state in few words, as I think 

 it may in a degree corroborate the theory for Avhich the agricul- 

 tural world is now so much indebted to the talented professor of 

 Geneva. 



I had observed two plots of raspberry-bushes, the soils and sub- 

 soils of which were very dissimilar, and situated some miles 

 apart; these I compared with a plantation of my own. The 



* Chondrilla miiralis is the Common Gum-Succory (vvhich in the 

 * Hortus Britannicus' of Loudon, is Chondrilla /wTzcea, oi* rush-leaved), — 

 Mercurialis annua is the annual Herb-Mercury. — This Author. 



