DEVELOPMENT OF FORM 



[CH. 



has been that of representing the principal energy of 

 further shoot development in the two directions of greater 

 elongation and of concentration of the shoots towards the 

 tips of their parent axes. The type is found commonly 

 enough in Willows and Poplars. 



Fig. 36. 



Now suppose we stop the growth in length of the 

 principal axis in Fig. 33, and direct the energy of growth 

 into a few only of the laterals as in Fig. 36, at the same 

 time favouring slightly the more outwardly directed off- 

 shoots. This rapidly leads to a form like Fig. 37, a type 

 characteristic of the Lime, some Elms, Hazel, &c. in 

 middle age. 



