Chap. III.] UPWARD GROWTH OF THE HEAD, ETC. 
87 
CHAP. III. 
UPWARD GROWTH OF THE HEAD, AND DOWNWARD 
GROWTH OF THE ROOTS. 
I have postponed the consideration of the up- upward growth 
of the head and 
ward growth of the head in elongation, in order downward 
growth of the 
to take it in coni unction with the downward roots considered 
° together. 
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 paragraph, 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 The upward 
growth of a 
with its downward growth, may be said to tree, or length- 
° ening of its 
resemble the growth of animals by intus-suscep- shoot, is by en- 
° j l largement of 
tion; that is, the growth of the shoots of the 
current year of the leader and branches, is a *"J e a ^ r ° f pro . 
growth or extension of parts already formed by ^“ s ar b * lily 
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 
