XIV 
INTRODUCTION. 
or torpidity supervenes ; this cannot be disturbed or has- 
tened without injuring the strength and vigour of the 
plant for the ensuing year. 
It will be found a great improvement to a fernery to 
introduce a number of mosses and Marchantise : the latter 
are particularly useful ; they speedily cover the earth and 
stones, and keep the surface in that state of moisture which 
is so very advantageous. All kinds of grasses, on the 
contrary, should be exterminated, for they are of so rapid 
a growth, and vigorous a nature, that they quickly over- 
power, weaken, and finally destroy the more delicate 
among the Ferns. 
There is one species, — Trichomanes speciosum, — which 
in some localities has its fronds always wet ; it generally 
grows within the spray of waterfalls, or in similar situa- 
tions, where it is constantly supplied with the needful 
moisture. This I find a most difficult situation to imitate, 
hut it may he managed by suspending above the Fern a 
vessel containing water, which shall he allowed to drop 
slowly on a stone, or other hard substance in the neigh- 
bourhood of the plant, the fronds of which vdll be wetted 
by the sprinkling caused by each drop. Polypodium Phe- 
gopteris and Cystopteris fmgilis benefit greatly by a 
similar treatment. 
There is one Fern, — Asplenium marinum, — which 
hitherto I have failed to cultivate in anything like its na- 
tural luxuriance : this species grows on the most exposed 
rocks on our bleakest shores, and yet I believe it has never 
been cultivated in the open air with success : in a tempe- 
