Chap. XVIII. FROM CHANGED CONDITIONS. 147 



plants propagated by cuttings, as with the Pelargonium, and especially the 

 Dahlia, manifest advantage is derived from getting plants of the same 

 variety, which have been cultivated in another place ; or, " where the 

 " extent of the place allows, to take cuttings from one description of soil 

 " to plant on another, so as to afford the change that seems so necessary 

 " to the well-being of the plants." He maintains that after a time an 

 exchange of this nature is " forced on the grower, whether ho be pre- 

 " pared for it or not." Similar remarks have been made by another excellent 

 gardener, Mr. Fish, namely, that cuttings of the same variety of Cal- 

 ceolaria, which he obtained from a neighbour, "showed much greater 

 " vigour than some of his own that were treated in exactly the same 

 " manner," and he attributed this solely to his own plants having become 

 " to a certain extent worn out or tired of their quarters." Something of 

 this kind apparently occurs in grafting and budding fruit-trees; for, 

 according to Mr. Abbey, grafts or buds generally take on a distinct variety 

 or even species, or on a stock previously grafted, with greater facility than 

 on stocks raised from seeds of the variety which is to be grafted ; and he 

 believes this cannot be altogether explained by the stocks in question being 

 better adapted to the soil and climate of the place. It should, however, 

 be added, that varieties grafted or budded on very distinct kinds, though 

 they may take more readily and grow at first more vigorously than when 

 grafted on closely allied stocks, afterwards often become unhealthy. 



I have studied M. Tessier's careful and elaborate experiments, 6 made 

 to disprove the common belief that good is derived from a change of seed ; 

 and he certainly shows that the same seed may with care be cultivated on 

 the same farm (it is not stated whether on exactly the same soil) for ten 

 consecutive years without loss. Another excellent observer, Colonel Le 

 Couteur, 7 has come to the same conclusion ; but then he expressly adds, 

 if the same seed be used, " that which is grown on land manured from the 

 (f mixen one year becomes seed for land prepared with lime, and that 

 " again becomes seed for land dressed with ashes, then for land dressed 

 " with mixed manure, and so on." But this in effect is a systematic 

 exchange of seed, within the limits of the same farm. 



On the whole the belief, which has long been held by many 

 skilful cultivators that good follows from exchangino- seed 

 tubers, &c, seems to be fairly w T ell founded. Considering the 

 small size of most seeds, it seems hardly credible that the ad- 

 vantage thus derived can be due to the seeds obtaining in one 

 soil some chemical element deficient in the other soil. As 

 plants after once germinating naturally become fixed to the 

 same spot, it might have been anticipated that they would 

 show the good effects of a change more plainly than animals, 

 which continually wander about; and this apparently is the 



6 'Mem. de 1'Acad. des Sciences,' 1790, p. 209. 



7 ' On the Varieties of Wheat,' p. 52. 



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