326 CHARACTEES OP TRIBES AND GENERA. 



the superior venules having unilateral sori as in true 

 Asplenium. 



The following species, taken from " Ferns, British and 

 Foreign," are sufficient to illustrate the genus. They are 

 widely diffused throughout the tropics of both hemispheres, 

 with the exception of D. thelypteroides, which is found in 

 North America. 



* Vernation erect. 



f- Fronds simple. 

 Sp. D. plantagineum, Sw. (v v.). 



ft Fronds pinnatifid. 

 D. Zeylanicum, Hook, (v v.). 



tff Fronds pinnate. 



D. pallidum, Bl. ; D. graiidifolium, Sw. (v v.) ; D. Jug- 

 landifolium, Sw. (v v.) ; D, alternifolium, Bl. (v v.) ; D. 

 fraxinifolium, Wall. ; D. celtidifolium, Kunze ; D. Lobbi- 

 anum, Hook. 



tttt Fronds lipinnatifid or Hpinnate. 

 D. Shepherdi, Link, (v v.) ; D. coarctatum, Link, (v v.) ; 

 D. striatum, Pr. (v v.) ; D. expansum, Willd. (v v.) ; D. 

 diversifolium, Wall, (v v.) ; D. conchatum, Moore (v v.) ; 

 D. polypodioides, Bl. (v v.) ; D. Schkuhri, Mett. ; D. 

 Klotzschii, Moore (v v.) ; D. lobulosum, Wall. ; D. costale, Pr. 



** Vernation decumbent. 



D. sylvaticum, Sw. (v v.) ; D. dilatatum, BL (v v.) ; D. 

 arbor escens, Sw. (v v.) ; D. vestitum, Pr. ; D. Thwaitesii, 

 J. Sm. (v v.) ; D. flexuosum, Pr. ; D. thelypteroides, Pr. 

 (v v.) ; D. Franconis, Mett. (v v.). 



