342 
FERNS : BRITISH AND FOREIGN. 
species of Davallia, and a few others. Their rhizomes 
remain perfectly naked during the winter, and seem 
to be constituted for a season of dry rest. 
These obversations are sufficient to show how 
certain species will grow under the most opposite 
conditions, and that a knowledge of them materially 
assists our efforts of cultivation, which I shall pro- 
ceed to treat of under two heads, — special and 
natural. 
II. Special or Pot Cultivation. 
W ITH the exception of those species sufficiently 
hardy to bear the cold of this climate, the 
whole family of Ferns can be artificially and most 
luxuriantly grown, under but two different scales of 
temperature, and with as little difference in other 
respects. There can be no better instance than that 
afforded by the immense collection now at Kew,* where, 
in the Tropical Fern-house, a great many species from 
various climates are placed under an average tempera- 
ture of 60° to 70°. In this housef are species from 
nearly all the tropical and sub-tropical countries 
of the world, and, being in one compartment, they 
are all alike subject to the same amount of atmo- 
spheric moisture as of heat. However, in respect 
to moisture supplied to their roots, the amount 
is varied according to the nature and require- 
ments of the plant. The same remarks apply to 
the Temperate House, of course with a reduction 
* May 1864. 
•f Length 130 feet, width 34 feet. 
