CHAEACTEF.S OF TOIBES AND GENERA. 335 



previously characterised under the name of Alliyrium, 

 which has been viewed by most authors as a section of 

 Asplernum, but which, for the sako of natural ai'rang-ement, 

 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. Henvidictyurii, Hook. Sp. Fit. 



Vernation fasciculate, erect, arboroid. Fronds pjinnate, 

 12 to l-i feet long ; pinnaa sessile cordate, from 1 to l-J- 

 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. A rpileniuni marginatum, Linn. 



Illust. Hook, and Bauer Gen. Fil., t. 65 A. ; Moore Ind. 

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

 Hook. Syn. Fil., t. 4, fig. 33 h. 



Obs. — This genus is founded on a magnificent Fern, a 

 native of Tropical America and West India Islands, having 

 a stem 5 to (! feet in height, bcaiing- a crown of pinnate 

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

 that distinguishes it from Allantodia, is in the indasium 

 being- plane and in the exterior margin of the reticulated 

 venation being comlaincd by a iransverse vein running- 

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

 ferences are scarcely sufficient to oharacteriae it as a genus 



