CHARACTERS OF TRIBES AND GENERA. 335 



previously characterised under the name of Athyrium, 

 which has been viewed by most authors as a section of 

 Asplenium, but which, for the sake of natural arrangement, 

 I have adopted as a genus, and restricting true Allantodia 

 to the present species. 



Sp. A. Brunoniana, Wall. 



Hab. A native of Ceylon, Nepal, and Java, also found in 

 Otaheite. 



193. HEMIDICTYUM, Presl (1836). 

 Asplenium, sect. Hemidictyum-, Hook. Sp. Fil. 



Vernation fasciculate, erect, arboroid. Fronds pinnate, 

 12 to 14 feet long ; pinnae sessile cordate, from 1 to 1 

 feet long, by 3 to 4 inches wide. Veins forked ; venules 

 parallel till near the margin, then anastomosing and reti- 

 culated, combined by a transverse continuous marginal 

 vein. Sporangia produced on the anterior side of the 

 parallel venules, constituting unilateral linear sori. In- 

 dusium plain. 



Type. Asplenium marginatum, Linn. 



Illust. Hook, and Bauer Gen. Fil., t. 55 A. ; Moore Ind. 

 Fil., p. 38 A. ; J. Sm. Ferns, Brit, and For., fig. 116 ; 

 Hook. Syn. Fil., t. 4, fig. 38 h. 



OBS. This genus is founded on a magnificent Fern, a 

 native of Tropical America and West India Islands, having 

 a stem 5 to 6 feet in height, bearing a crown of pinnate 

 fronds, measuring 12 to 14 feet in length. The chief point 

 that distinguishes it from Allantodia is in the indusium 

 being plane and in the exterior margin of the reticulated 

 venation being combined by a transverse vein running 

 parallel with and close to the margin. These slight dif- 

 ferences are scarcely sufficient to characterise it as a genus 



