CULTIVATION. 
385 
number of species of exotic Ferns sufficiently hardy 
to bear the cold of our winters is very limited, much 
less than is generally believed, the chief of them 
being natives of North America, which, with the 
British species, amount to about 80 in all; therefore 
the extent of space required for a simple collection of 
hardy Ferns is small; an area of 60 feet by 10 will be 
ample, and which may be either on the side of a slope, 
or between two slopes with a path in the centre and 
open at one end only ; or it may be a raised oblong 
mound with a path all around it. If not confined to 
a strictly scientific collection, and space to be had, an 
interesting natural glen may be formed by introducing 
other plants conspicuous for their large foliage. 
It has been already stated, that although our small- 
growing native and several exotic species, such as the 
rock Asplenice, Woodsia, &c., endure the extremes of 
heat and cold in their native localities, they neverthe- 
less suffer by full exposure under artificial cultivation ; 
it is therefore necessary to jilant them on the rockery, 
so that they can readily be protected in winter; an 
inverted flower-pot, placed over each plant and covered 
with leaves, or some loose material analogous to the 
covering of snow of their native country, is a good 
protection against being injured by excess of moisture 
or severe cold. Where the rockery is to be carried 
out on a large scale, then oaves and chasms may readily 
be constructed, and with a natural or artificial head of 
water they can be kept moist by the constant drop- 
ping and spreading spray; thus making appropriate 
positions for the natural growth of Adiantum Cappilus, 
Hi/menophyllece, &c. But when a full collection of the 
many varieties of Sculopendrium, Axplenium, Lomaria, 
2 c 
