100 RELATION OP PHYLLOTAXIS TO MECHANICAL LAWS. 



Fig. 40. — Araucaria excelsa, E. Br. Transverse section of the growing point of a 

 lateral branch, system (8 + 13), camera lucida drawing. The origin of branches 

 of the next degree follows definite lines ; the first leaves of these ajses are repre- 

 sented in outline only. 



