^8 STRUCTURE OF VESSELS. 



many valuable crooks g, h, i, will be formed above 

 the knees. It is necessary, however, to guard 

 against training the branches to too great a height, 

 as, when so, they run much risk of being twisted and 

 torn by high winds. 



Knees may also be obtained by cropping the top 

 from plants that have side branches similar to 

 and training these branches for leaders as above di- 

 rected. In this case, the section, where the top is 

 cut off, must not be too large, and the branches, 

 either two or four, well knotted to the trunk, or the 

 situation sheltered, otherwise the trunk at the sec- 

 tion may be split down by the strain of the wind on 

 the new leaders. Also, in healthy growing trees of 

 considerable size, which have spreading tops, and 

 which are not to be cut down for a considerable time, 

 the forester, if he have a good eye, may, by lopping 

 off a few branches here and there throughout the top, 

 throw the greater part of the boughs into condition 

 to become knees, or valuable crooks, when of size. 

 This is of most material consequence to the ulti- 

 mate value of half-grown oak trees, in open situa- 

 tions, and ought to be particularly studied by the 

 superintendent, as, when allowed to run into very 

 numerous stemmy branches, without direction or cur- 

 tailment the top, instead of being ultimately of con- 



