Chap. I] CHARACTERS OF THE TROPICAL CLIMATE 229 



Mainly, but not exclusively, tropical are the Cyatkeaceae, to which almost 

 all tree-ferns belong (species of Cyathea, Dicksonia, Alsophila), and the 

 Hymcnophyllaccac, small, frequently moss-like herbs with transparent 

 foliage, which cover stems of trees and rocks in moist, shady forests, just 

 as mosses do with us. 



The great mass of tropical ferns belongs to the order Polypodiaccae, which 

 is also so strongly represented in Europe, and to a considerable extent by 

 the same genera, namely Polypodium, Aspidium, Asplenium, Pteris, and 

 so on. Only a few rare Polypodiaceae are tree-like. 



Fig. 116. Forest landscape in the Seychelles. In the foreground, Gleichenia linearis; in the 

 background, palms (probably Koscheria melanochaetes, H. Wendl.), Pandanus, and other plants. 

 From a photograph by A. Brauer. 



The Lycopodiaceac are much less prominent than the ferns, but neverthe- 

 less of greater significance than in temperate floras. Species of Selaginella 

 often form the chief covering of the forest soil ; Lycopodium cernuum is 

 extremely common in well-lighted spots ; other species of Lycopodium as 

 well as of Psilotum are occasionally common epiphytes. 



The Eqitisctaccac are not more strongly represented than in the 

 temperate zones. 



