34 HISTORY OF BRITISH FERNS. 
marks left on the falling away of the fronds ; they grow 
to a height of from twenty to fifty feet or more, from their 
tops sending out the feathery fronds, often many feet in 
length, and yet so delicate as to be put in motion by the 
gentlest breeze. On some of the East-Indian Islands the 
tree Ferns are said to occur as numerously as the crowded 
Firs in our plantations; but wherever they are found— 
from the plains to an elevation of 3000 to 4000 feet— 
the soil and atmosphere are full of moisture. Very noble 
arborescent Ferns are also found in New Zealand and 
Tasmania. 
The shrubby Ferns, those with short stems, surmounted 
by tufted fronds, prevail rather at the tropics than at the 
equatorial zone, and are found less frequently at the foot 
of tropical mountains than at an elevation of from 2000 to 
3000 feet. Ferns of this aspect abound in the South Sea 
Islands. Mr. Colenso describes one of the New Zealand 
species as producing, from a main trunk twelve feet high, 
fronds which form a droop often of eighteen feet; such 
plants, standing singly on the bank of a stream, being 
objects of surpassing beauty. 
The dwarf herbaceous species are rather characteristic 
of the temperate and colder zones : not that their number 
