Chap. I] CHARACTERS OF THE TROPICAL CLIMATE 227 



able influence on the facies of the forest, than we ever do in the virgin forests of 

 Brazil. There, nothing is to be found comparable with the gaily coloured clumps of 

 the numerous Hymenomycetes of our forest soil. The first impression which a fresh- 

 comer wandering in a Brazilian forest must receive, is that apparently very few 

 fungi occur there. As a matter of fact this is in reality not the case ; the fungal flora 

 is extremely rich, but the minute forms especially appear in great abundance, and 

 these are seen only when one looks carefully for them, while the larger forms for the 

 most part only occur here and there V 



Among Lichenes, the Ascolichenes, at any rate as far as number and size 

 of individuals go, play a much smaller part than with us. Large tufted 

 forms, such as Usneae, are seen only on high mountains and therefore 

 outside the megathermic climate. Cora Pavonia, which alone forms the 

 class of Hymenolichenes, is exclusively tropical, and appears to be cos- 

 mopolitan within the tropics. It is found in its various forms of growth, 

 but chiefly in its proper Cora-form, in abundance on moist soil and on the 

 bark of trees. 



Bryophyta. 



Among Bryophyta, and especially among Musci, megatherms are rare, 

 and are represented for the most part by small inconspicuous species which 

 occur scantily in cool damp situations, and are quite unimportant in their 

 effect on the general facies of the vegetation. Much more richly do they 

 appear in the cool regions of tropical mountains 2 . 



Pteridophyta. 



Ferns in the tropics develop an extraordinary wealth of form, and vary in 

 their dimensions from small moss-like plants to trees. Most of them are 

 hygrophilous and shade-lovers, so that only humid forests show a great 

 richness in ferns. Besides, the majority of them are not decidedly mega- 

 thermic, but prefer a climate that is mild, even if it be as uniform as 

 possible, so that the greatest development of ferns in numbers, especially 

 of their arborescent forms, is exhibited less in the lowlands than in cooler 

 mountain landscapes. 



Three orders of ferns are exclusively tropical, the Gleicheniaceae, 

 Schizaeaceae, and Marattiaceae. 



The Gleicheniaceae are repeatedly branched in a dichotomous manner ; 

 they present a very unique appearance, and in contrast with most of their 

 tropical allies, these ferns occupy open sunny situations, and usually are 

 in large numbers together. This last statement is specially true of the 

 almost cosmopolitan Glcichenia linearis (Fig. 116), which is common 

 everywhere. 



The Schizaeaceae (for example Aneimia, a xerophilous genus chiefly in 



1 Alf. M oiler, op. cit.. p. 154. " See Sect. IV. 



Q 2 



