186 A TEXT-BOOK OF BOTANY 
though ferns are found in considerable numbers in temper- 
ate regions, their chief display is in the tropics, where they 
form a striking and characteristic feature of the vegetation. 
In the tropics not only are great masses of the low forms 
to be seen, from those with delicate and filmy moss-like 
leaves to those with huge leaves, but also tree forms with 
Fia. 178.—The staghorn fern, wuicu is an epippy te. 
eylindrical trunks encase:l by the rough remnants of fallen 
leaves and sometimes rising to a height of thirty-five to 
forty-five feet, with a crown of great leaves fifteen to 
twenty feet long (Fig. 177). There are also air forms 
(Fig. 178), that is, ferns that perch upon other plants but 
