340 
FERNS : BRITISH AND FOREIGN. 
as may be seen in some of tbe nurseries and market- 
gardens near London, it produces fronds 2-3 feet in 
length. The Asplenium Trichomanes , A. JRuta-muraria , 
Ceterach officinarum, and Poly podium vulgare, are also 
wall and tombstone-lovers, and may be called our 
domestic Ferns. 
Another remarkable example of a Fern making 
itself at home under extremes of temperature and 
moisture, is Pteris longifolia, a species having a wide 
range throughout the tropical and sub-tropical regions 
of both hemispheres. On the island of Ischia (Bay 
of Naples) it is found luxuriating within the influence 
of the hot vapours rising out of the cavities left by 
extinct volcanoes, growing in soft muddy soil at a 
temperature ranging from 140° to 160°. In our 
hothouses its spores vegetate abundantly upon all 
moist surfaces, and in the crevices of brick walls. * 
Plants of it are nearly always to be found over the 
openings of hot-water tanks, and it has been seen 
in crevices of the walls outside hothouses, or even 
under iron gratings, where it could receive but little 
light, and where the temperature was often near the 
freezing-point. In the dry air of the Cactus-house 
plants of it have produced fronds from 2-3 feet in 
length. 
In general the fronds of Ferns remain long in a 
perfect state; the exceptions to this rule are com- 
paratively few, and these are chiefly supplied by the 
natives of climates alternating with seasons of heat 
and cold. But as many species are wanderers and 
conform to the effects of various climates, it is no 
wonder to see some of our native Ferns assuming 
the evergreen habit of their foreign allies, when 
