INTRODUCTION. 
XXIX 
state of perfect quiescence. In closed cases we thus not 
only avoid rapid changes of temperature, hut the active 
motion in extremes of temperature, which is the most in- 
jurious property of such extremes. The deleteiious effect 
of boisterous winds on the fragile fronds of ferns needs no 
exemplification ; it is so great, that if a specimen of Cys- 
topteris he moved from its protected habitat, and placed 
where it may receive the full force of the wind, that alone 
will, in a few weeks, work its utter destruction : to such a 
plant how grateful must be the motionless atmosphere thus 
provided ! 
The solution of the problem appears to me to he simply 
this : that while the power of destructive natural agents is 
restrained, that of beneficial natural agents is retained, and 
its efficacy ensured. 
Carrying out the system, nothing is more easy than to 
raise any species of Fern from the seed, which every her- 
barium affords abundant opportunity of procuring; and 
thus Ferns from every country may he assembled in our 
houses, with even less trouble than by transporting the 
roots in cases. The seeds should be first detached from 
the frond by gently rubbing the clusters of capsules, and 
then shaken on a common plate ; next, having procured 
some light sandy earth, crumble it on the plate, and shake 
it about for a minute or two, when all the seeds will be 
found adhering to the little masses of earth ; spread this 
earth, as lightly as may he, over other light sandy or loamy 
earth, either in a garden or in a flower-pot, in doors or out, 
always taking care very carefully to cover the seed with a 
