326 CHARACTERS OF 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. 
+ Fronds simple. 
Sp. D. plantagineum, Sw. (v v.). 
tt Fronds pinnatifid. 
D. Zeylanicum, Hook. (v v.). 
ttt Fronds pinnate. 
D. pallidum, Bl.; D. grandifolium, 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 bipinnatifid or bipinnate. 
D. Shepherdi, Link. (v v.) ; D. coarctatum, Link. (v v. 
D. striatum, Pr. (v v.); D. expansum, Willd. (v v.); | 
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, 
| ** Vernation decumbent. parn 
D sylvaticum, Sw. (v v.); D. dilatatum, Bl. (v v-) i 
~ arborescens, Sw. (v v.); D. vestitum, Pr.; D. Thw 
T. J. $m. (v v.) ; D. flexuosum, Pr.; D. tbelyptetcid 
v y) Dy Geen? Mett. (v v). 
