CHARACTERS OF TRIBES AND GENERA. 351 



203. LYGODIUM, Sw. (1800). 

 Hook. Syn. Fil. 



Vernation uniserial, distant and sarmentose, or contiguous 

 and csespitose. Fronds scandent, twining, extending to an 

 indefinite length ; pinnae conjugate, palmate lobed, pinna- 

 tifid or pinnate. Veins forked, free. Sporangiferous 

 epikelets marginal, composed of two rows of imbricate 

 indusaeform cysts, each cyst containing an oval, resupinate 

 sporangium attached by its inner side, and opening length- 

 wise on its outer side. 



Type. Lygodium circinatum, Sw. 



Illust. Hook, and Bauer, Gen. Fil., t. 28 ; Moore, Ind. 

 Fil., p. 90 B. ; J. Sm., Ferns, Brit, and For., fig. 141 ; 

 Hook., Syn. Fil., t. 9, fig. 68, a, b, d. 



OBS. The Ferns constituting this genus are readily 

 known from all others by their climbing habit ; the fronds 

 being permanent, and increasing in length indefinitely by 

 their twining and interlacing with one another, and with 

 other plants, they form impervious thickets. The various 

 forms they assume, and the divisions of the fronds, render 

 it difficult to arrive at any satisfactory conclusion as to the 

 number of distinct species. Presl enumerates forty species, 

 but in the " Synopsis Filicum " only sixteen are described, 

 which I consider to be nearer the true number of distinct 

 species. They abound within the tropics, and extend to 

 New Zealand in the southern, and L. palmatum extends to 

 Canada in the northern hemisphere. 



* Petiole of pinnules articulate with the rachis. 



Sp. L. articulatum, Rich, (v v.) ; L. scandens, Sw. (v v.) ; 

 L. venustum, Sw. ; L. volubile, Sw. ; L. pinnatifidum, Sw. 

 L. polystachyum, Wall, (v v.). 



