90 BRITISH FERNS. 



rock, in which its roots had no kind of hold ; this was the charac- 

 ter of the plant when most luxuriant, but I found other and 

 much smaller plants which possessed more root and less rhizoma, 

 and the roots were fixed in a thin layer of moist earth, among a 

 profusion of moss and Hymenophyllum. 



The fronds make their appearance in summer ; as late as the 

 beginning of August I found many fronds in the young state, 

 shewn to the left of the illustration, by which it will be seen 

 that the pinnae are individually circinate, as well as the entire 

 frond. It must be at least as late as October before the fronds 

 arrive at maturity; and I found those of the previous year, 

 very dark coloured indeed, but quite unfaded at the time of 

 my visit. 



The form of the frond is triangular, the apex being elongated 

 and pointed ; it is pinnate, the pinnae being also pinnate, and 

 the pinnulae pinnate : perhaps it would be more correct to 

 describe the hard wiry stem-like veins as thus divided, and to 

 say that each of these veins is furnished on each side with a 

 semimembranous wing, extending throughout its length, for 

 this is the case. The entire frond is composed of these wings, 

 and all its divisions are consequently narrow and linear ; the 

 wing is without visible veins of any kind. The figure represents 

 the plant of less than the natural size. 



This genus comprises many very beautiful exotic species, 

 principally inhabitants of tropical climates : in some of the West 

 India Islands they clothe the trunks of trees with a most graceful 

 and elegant drapery. The mode of fructification in T. spe- 

 ciosum is very singular. The mass of thecae is attached to the 

 centre of a vein, after its ultimate division, and invariably to 

 that one which is situated nearest the midvein of the frond, pinna 

 or pinnula, as the case may be. At the attachment of this mass 

 of thecae the wing loses its green and semimembranous appear- 

 ance ; its cuticles separate, and form an elongate cup-shaped 

 receptacle, which includes the mass of thecae. The vein itself, 

 after bearing the thecae, runs through the receptacle, and 

 projects considerably beyond its extremity, in the similitude of 

 a bristle. 



This definition of the generic characters appears to me the 

 correct one, but I subjoin that given by Sir J. E. Smith, not 

 simply on account of its remarkable discrepancy with my own 

 view of the structure, but because it is the one usually received. 



