CHABACTEES OF TRIBES AND GENEEA. 611 



186.— Athteium, TuAli. (1788). 



Allantodia sp., li. Br., 1810 ; Asidcniiim sp. aucL, sect. Atli.ij- 

 rium, Hook. Sp. Fil., J. Sm,. Ferns Brit, and For. 



Vernation fascicalate, erect or decumbent, solitary or 

 becoming ca3spitose. Fronds bi-tripiunatifid, 1 to 4 feet 

 bigli, ultimate segments dentate, or deeply laciniated. Veins 

 forked ; venules free. Sporaiijia unilateral, or often bi- 

 lateral on tke lower exterior venule. Ind.nsium generally 

 vaulted, sing-le or binate, or oblong reniforme, forming 

 linear, straight, or curved, generally unequal-sided sori. 



Type. Aspleiiiuin Filix-feemina, Bernh. 



Illust. Hook, and Bauer. Gen. Til., t. IG ; Moore Ind. 

 FiL, p. 37, A. ; Hook. Syn. Fil., t. 4, fig. 38, E. 



Oes, — The form of tlie sori in the species included in this 

 genus is very variable, some being unilateral as in Axple- 

 nium, others binate as in Biplaziimi, while in others the 

 iudusium is oblong roniform as in Fadyenia, but the lobes 

 are generally unequal, such differences being in many 

 instances found in the same frond. In many the indusium 

 is cylindrical and vaulted like that of true Allantodia. 



In the "Species Filicum," as well as in "Ferns, British 

 and Foreign," Aihyrium is. ranked as a section of y^.s^)fe/?M(nz, 

 but, for the sake of a more natural grouping- of species, I 

 deem it best to allow it to rank as a genus ; more distin- 

 guished by its habit of growth and the soft and brittle 

 nature, and highly compound character of the fronds, than 

 by the character of the sori ; and the species may be viewed 

 as having more relationship with the compound-fronded 

 species of Diplazium than with Asplenium. 



In the " Species Filicum " twenty-nine species are enu- 

 merated, but in the " Synopsis " the number is reduced to 

 nineteen, ten of which have come under my observation in 



