Conditions of the Growth of Plants. 93 



for this capability of adapting itself to new circumstances, it 

 could not thrive in Northern America ; since its own powers of 

 growth would be insufficient, when its external conditions are 

 so much changed. It is this capability which renders it so 

 useful. If large potatoes raised in northern countries be planted 

 again in tropical climates, they at once dwindle, and their 

 produce becomes little superior to that of the original stock ; 

 since when circumstances no longer demand it, the acquired 

 habit ceases. The Cabbage, Broccoli, and Cauliflower are, in 

 like manner, only varieties of a single species, greatly altered by 

 cultivation and change of circumstances ; the plant which was 

 the original stock of all having been found susceptible of 

 enduring such changes, and thus rendered at the same time 

 useful and easy of production. The celery which is in such 

 common use on our tables, in its original state is a small, rank 

 coarse plant, wholly unfit for eating. By causing it to grow in 

 a peculiar manner, it becomes sweet, crisp, juicy and agree- 

 able. 



These instances, to which many others might be added, will 

 suffice to show that not only in their original state is exhibited 

 the adaptation of each tribe of plants to particular circumstances, 

 but that there are many which can thus spread themselves, or 

 be spread by man, over a large portion of the globe. In this 

 capability, no less than in their native aspect, do we recognise 

 the wisdom and power of the Almighty, who willed that no 

 portion of the globe should be unclothed by vegetation, and 

 that from every place should spring forth herbage for the animal 

 creation, which is entirely dependent on it, either directly or 

 indirectly, for its sustenance. Such, then, being the universal 

 diffusion of plants, it is obvious that in no spot can he who 

 seeks to make himself acquainted with their structure and 

 habits, be without some subjects for examination; and since 

 the humblest and simplest of these beings are found to display 

 an organization as remarkably and beautifully adapted to the 

 functions they are to perform, and to the conditions in which 

 they are to exist, as is that of the highest and most complicated, 

 there is no reason why any, however insignificant they appear,' 

 should be neglected. 



