33 



pared 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 ex- 

 tension 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 upwards, or by what may 

 be more properly called intus-suscep- 

 tion. I have observed this in plants 

 which I had introduced through the 

 window-sill, and trained against the 

 shutter, by marking the position and 

 upward progress of the stalk of each leaf 

 where it joins the stem. Duhamel first 

 pointed out this fact. With the excep- 

 tion of the parts of the shoot of the 

 current year, no other part of a tree makes 

 any upward progress. 



The downward growth of a tree, that is, 

 c 



