80 



UPWARD GROWTH OF THE HEAD, AND pt. ii. 



CHAPTEE III. 



GROWTH OF THE ROOTS. 



Upward 

 growth of 

 the head 

 and down- 

 ward 

 growth of 

 the roo's 

 considered 

 together. 



The 

 upward 

 growth of 

 a tree, or 

 lengthen- 

 ing of its 

 shoot, is by- 

 enlarge- 

 ment of all 

 parts of 

 that shoot; 

 and all 

 parts of 

 these parts 

 progress 

 bodily 

 upwards. 



I HAVE postponed the consideration of the upward 

 growth of the head in elongation, in order to take it in 

 conjunction with the downward growth of the root in 

 elongation ; because I think that each may be better 

 understood by contrast with the other. This is a 

 deviation from the order laid down in an early para- 

 graph, but I leave that paragraph unaltered, because I 

 think it may give the beginner a clearer idea of which 

 growth is supposed to result from the upward sap, and 

 which from the downward sap. 



The upward growth of a tree, as compared with its 

 downward growth, may be said to resemble the 

 growth of animals by intus-susception ; that is, the 

 growth of the shoots of the current year of the leader 

 and branches, is a growth or extension of parts already 

 formed by the upward and outward increase of all 

 those parts from within. Besides the growth at their 

 ends, all the parts of the shoot of the current year, to a 

 certain degree, grow bodily upw^ards, or by what (by 

 comparison with the downward growth) may be called 



