92 
BRITISH FERNS. 
of many "hundred or even thousand feet above the sea- 
level, and some even select the craters of volcanoes for 
their home, those of Pinchincha, near Quito, and of St. 
Vincent’s Island, each having its especial fern as denizen. 
They are as variable in choice of soil as in their other 
predilections. Some, as the Polypodium Robertianum 
and Nep hr odium rigidum , cannot live except on lime- 
stone ; others, as the Allosorus crispus, prefer anything 
to lime ; some require bog earth ; some seem to object 
to the presence of any earth at all, planting themselves 
in such narrow fissures or mere cracks in the rocks that 
it seems impossible that any room at all can be found 
for earth ; and others growing parasitic on the bark of 
trees, seeming to draw their entire nourishment from 
the surrounding air. 
The proportion that ferns bear to flowering plants 
varies in different countries. In England there is one 
fern to thirty-five flowering plants ; in Scotland one to 
thirty-one. In Jamaica ferns form one-ninth of the 
«/ 
flora, in New Guinea one-fifth, in Ireland one-sixth, in 
the Sandwich Isles one-fourth, in equinoctial America 
one thirty-sixth, in Portugal one hundred and sixth, in 
Greece one to two hundred and twenty-seven, in Green- 
land one to ten, at the North Cape one to seven, in 
Sweden one to eighteen. 
This table, which we take from Mr. Moore’s c Hand- 
book,’ demonstrates that ferns bear a much larger pro- 
portion to flowering plants on islands than on continents 
— Ireland and the Sandwich Isles showing the highest 
proportion, only nearly equalled by Greenland and the 
North Cape, where the floral vegetation is at the lowest. 
There is no doubt that the atmosphere preferred by the 
majority of ferns is a calm damp one; it is only in very 
