CULTIVATION. 307 



grown in a temperate house ; of whicli Polysticlmm 

 aculeatum, Lastrea dilatata, and L. Filix-mas may be 

 cited as examples^ as also Asplenium marinum. In 

 1820 I found plants of it, having fronds from 2-4 

 inches in length, growing in a cave facing the German 

 Ocean, on the east coast of Scotland ; of these, two 

 plants have been grown at Kew from that time ; of 

 late years, one in the Temperate and the other in the 

 Tropical House. These became fine caespitose plants, 

 with fronds varying from 1-1 ^ foot in length; the 

 greatest length beiag attained by the plant in the 

 Tropical House, even assuming the character of a 

 species native of the West Indies and Tropical 

 America, and quite unlike the original plant; thus 

 showing that although at home in the cold, sunless 

 cave, it can well appreciate a better fed and warmer 

 abode. Exceptions to this rule are some alpine 

 species. Ferns in that respect being analogous to our 

 ill success in Rowing many alpine flowering plants. 

 This is no doubt partly owing to the difference of 

 atmospheric density, and the varying influences of 

 temperature and moisture common to the sea-level of 

 this climate. 



The species of cold climates truly deciduous, produce 

 their fronds from an underground creeping sarmentum, 

 of which Pteris aquilina, SitoloMum punetilobium, 

 Onoclea sensihilis, Anchistea virginiaa, Lorinseria areo- 

 lata, Leiicostegia immersa, and Phegopteris aurita are 

 the principal examples. On the other hand, instances 

 of tropical species periodically losing their fronds 

 without any apparent cause, such as by undue excess of 

 heat and moLsture, are Phymatodes oxyloba, Pleuridium 

 palmatum, P. venustum, Vrynaria propinqua, several 



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