214 Dr. Mac Culloch on the 



Thus I may terminate this subject as it regards Guernsey, and 

 the conclusions which may be drawn from the peculiar character 

 of its vegetation. But on the probable or possible subject of 

 naturalization, it must yet be added, that the experiments on 

 seedling vines seem also to prove that such an effect does really 

 take place ; as, in many instances, the fruit of those has been 

 found to ripen with greater facility and certainty than that of the 

 ordinary plants from cuttings. The whole question must, how- 

 ever, remain for further examination. Did it only concern this 

 question, the increased facility of producing grapes out of doors, 

 it would be amply deserving of much fuller trials than have yet 

 been made ; while, when it is recollected how much it interests 

 the far more important question of the potatoe, particularly as 

 this relates to its cultivation in the wretched climates of Scotland, 

 there is nothing in the whole range of horticulture that is more 

 truly deserving of a serious course of experiments; a course which 

 should be indeed undertaken as to many other plants before we 

 reject the belief altogether. 



It is certain, as a general principle, that different plants vary 

 very much as to their sensibility respecting cold ; even when we 

 can discover no reasons in their constitution, their structure, or 

 their general physiology, why it should be so ; and, similarly, 

 where these natural affinities, or family connexions, and not less 

 their native climates, afford no ground for any priori judgment as 

 to this. The examples would be as endless to quote as they are 

 familiar. Is this a case, sometimes, of mere sensibility, of the action 

 on a nervous power, if I may use such a term, a power of which 

 the existence seems proved by their sufferings from various 

 poisons ? And if so, is it possible to change that constitution, as 

 it appears to be susceptible of being changed in animals by 

 habit ? In animals, the organization remains the same, but the 

 sensibility is diminished, while probably, possibly, the heat-gene- 

 rating power is augmented. Here perhaps one difficulty may lie, 

 as it certainly does, in the extreme case, as to vegetables. It is 

 more than doubtful whether they do generate heat ; and if this 

 were necessary, we should be disappointed. But if not, and if 

 the effect be an effect on their sensibility or nervous system, and 



