14 
CHOICE BRITISH FERNS. 
wliicli are thrown off year after year, and the, facility with 
which they can he transported by the wind, and by other 
means, this isolation or confinement to special localities is 
very remarkable. It can hardly be imputed to subtle local 
influences in the soil, as, under cultivation, the spores gene- 
rally germinate with the usual treatment, and the plants 
retain their peculiarities when transplanted. 
The entire absence of some species in many localities and 
spots which seem exactly fitted for them, is another peculiar 
feature. The common Hartstongue, for instance, is a com- 
paratively rare plant in Scotland, although one would expect 
to find it in profusion in the innumerable glens which abound 
there, and which seem the very heau ideal of a habitat for 
it. Tet this Fern is one of the least dainty in its require- 
ments, seeming to have no antipathy in the matter of soil 
or position, and in many localities thriving in abundance 
under the most diverse conditions, either in a small state, on 
dry, exposed walls, or throwing up huge fronds in the shady 
woods, where it can revel in abundance of leaf-mould and 
moisture. We are inclined to think that the greater or less 
predominance of certain forms of minute insect life may 
account for these peculiarities of habitat. Just as we find 
in our gardens that certain vermin attack and destroy certain 
plants, so it is only reasonable to assume that either the 
spores or the prothalli of these Ferns are the favourite food 
of some of the minuter insects, in order to explain the 
absence of adult plants. Climatal conditions are, of course, 
a potent factor, but do not account for all the phenomena 
observed. Some exotic Ferns it is quite impossible to grow 
unless isolated, slugs or snails being attracted from a con- 
siderable distance, presumably by some odour; Camptosorus 
rhizophyllus^ (an exotic Hartstongue) suffers thus. Other 
plants are specially subject to the attacks of woodlice; and 
as, doubtless, such special appetites characterise also the 
minuter and microscopic insect world, and as it is manifest, 
when we consider the myriads of spores which are shed in 
Syn. Seolopendrium rhizophyllum. 
