402 



NOTES AND ILLUSTRATIONS. 



light. Their stems were speedily elongated ; their bark became 

 smoother ; their side branches more slender, and thinner in spray 

 and foliage ; and by 1816 — that is, after seven years — they could 

 scarcely be recognised as the same plants. Soon after the fall of that 

 season, I once more transferred them to the open field. Here, 

 although they carried a good leaf, they appeared for some time 

 altogether stationary in their progress, as was to be expected. In 

 the absence of the shelter and warmth which they had so long 

 experienced, they could not at once generate provisions to enable 

 them to resist the cold : but in consonance to that law of nature 

 by which " plants, as well as animals, accommodate themselves to the 

 circumstances in which they are placed," they began gradually but 

 slowly to generate them ; so that it was only in 1824 that I observed 

 the trees to display any decided symptoms of induration of bark, 

 increase of roots, stoutness of stem, and closeness of ramification, 

 which constitute such provisions — and it is evident that it will require 

 some years more to effect a complete renovation of their former 

 character. 



From this short account we may perceive, that while trees retain 

 their full vigour — that is, while they continue in a rapidly progres- 

 sive state — they may be made alternately to assume or lay aside 

 those properties which best fit them for removal. Moreover we see, 

 that, as vegetation is always greatly more active in shelter than in 

 exposure, the properties just now mentioned — that is, the protecting 

 properties — are far more slowly obtained or reassumed than the non- 

 protecting. From such facts and experiments, therefore, as well as 

 from analogy, we are warranted to conclude, that the doctrine held 

 forth in the text is fully confirmed — namely, that "by the law of 

 nature, shelter and exposure — that is, heat and cold — ^have the power 

 alike of diminishing or increasing, of bestowing or taking away, 

 what may be called the protecting properties." 



