IN THE PRIMEVAL FOREST 223 



condition to form the wood of the tree. There is 

 no time to waste, for cold weather follows quickly 

 and the wood must be hardened and the buds 

 completed before winter. 



In the tropics conditions are very diflferent. 

 The summer is the period of growth, as in the 

 Temperate Zone, and during the balance of the 

 year most of the vegetation is more or less dor- 

 mant, also as in the temperate regions. But 

 there is no cold weather in the tropics and a large 

 proportion of the trees retain their leaves through- 

 out the year; in other words, they have persistent 

 foliage. The leaves, then, must do duty for sev- 

 eral years and they must be made to last and 

 stand hard service. Having to endure long dry 

 seasons, they are usually rather small, their upper 

 surfaces are smooth and glossy, their substance is 

 thick and leathery, their edges are entire. In dry 

 weather they close their pores, and probably add 

 a little to the coat of varnish on the upper sur- 

 faces; then they practically cease all functions. 

 They do finally grow old and wear out, falling 

 most abundantly dvuing the seasonal rains. One 

 reason they are so hard and glossy is to resist the 

 constant attacks of insects. 



