972 



A TEXTBOOK OF THEORETICAL BOTANY 



to grow, depends naturally on the particular ptyxis, and the appearance and 

 relationships of the voung leaves at this time are called the vernation (Figs. 

 962, 963 and 964). 



I 



Fig. 963. — Fraxiiius excelsior. Vernation of buds showing expanded 

 bud scales and pleated arrangement of young foliage leaves. 



Fig. 964. — Acer pseudoplatanus. Vernation of bud showing 

 folded young foliage leaves and terminal inflorescence. 



Leaf Duration. 



The duration of leaves, at least in perennial plants, is usually short com- 

 pared with the life of the plant which bears them. Deciduous leaves live for 



