230 PHYSIOLOGICAL BOTANY. PART II. 



generally become more or less rotten at the exposed 

 extremity before the new tissue has had time to coat it 

 over. Of all descriptions of wounds those which are 

 the nearest to the main stem heal the quickest, and 

 this shows us the propriety of pruning as close as pos- 

 sible to the trunk, whenever a branch is to be removed 

 for the purpose of improving the timber. The new 

 tissue increases with great rapidity chiefly from above 

 downwards, but also from the sides of the wound, and 

 a little likewise at the base, until it has spread over the 

 whole surface. The extent of the injury introduced 

 into the timber is best seen by forcibly separating the 

 new wood from the surface over which it has spread ; 

 when the latter will always be found exactly as it was 

 left at the time it was covered up, with the mark of the 

 knife upon it or with any portions of decay which may 

 afterwards have taken place. This is sometimes seen 

 in trees upon which deep inscriptions have been carved. 

 Wherever the letters have penetrated below the bark 

 into the woody layers an impression is left in them ; and 

 however long the new wood may have been formed 

 over them, they will be found beneath it whenever the 

 outer portion is removed. Birds' nests, stags' horns, 

 an image of the Virgin Mary, and many other articles 

 are described as having been found in the very heart of 

 some trees, where they were unquestionably embedded 

 by the enlargement of the stem in the way we have de- 

 scribed. 



(226.) Precautions to be observed in Prwniuj. 

 From what we have stated it is evident, that wherever 

 a branch has been pruned off a blemish is inevitably 

 introduced ; and consequently where pruning can be 

 avoided 'it should never be resorted to ; but where it 

 is really necessary it should be performed as early as 

 possible, before the branch has attained any consider- 

 able dimensions. Even rubbing off the buds should be 

 preferred to regular pruning. The cut also should be 

 made close to the stem, and as nearly vertical as pos- 

 sible; the latter precaution prevents the accumulation 



