160 J. SMITH ON THE GENERA OF FEHNS. 



duced to place them under Casseheera ; but setting habit 

 aside, the formation of the sorus in some of the species is 

 scarcely sufficiently distinct from Pteris as here restricted. 



53. Platyloma, J. Stn. 

 (Pterideae sp. Auth. Allosoreae sp. Presl.) 



Veins forked ; venules direct, their apices free and sporan- 

 giferous. Sori oblong, laterally confluent, constituting a 

 broad continuous compound marginal sorus. 



Fronds pinnate or bipinnate ; stipes generally ebeneouSf 

 smooth, pilose or sguamiferous. Pinnae articulated with the 

 rachis. Sporangia occupying a portion of the upper part of 

 the venules which by their closeness to one another, form a broad, 

 compound receptacle, with the indusium attached transversely on 

 its outer margin, 



Examp. 1. P. Brownii, J. Sm. (Adiantum paradoxum, 

 R. Br. Pteris latizona, A. Ciinn.) 2. P. falcata, (R. Br.) 

 3. P. rotundifolia, (Forst.) 4>. P. albida, (A. Cunn.) 5. P. 

 atropurpurea, (Linn.) 6. P. sagittata, (Cav.) 7. P. cor- 

 data, (Cav.) 8. P. andromedsefolia, {Kaulf.) Illust. Hook. 

 gen.Jil. ined. 



Obs. The ebeneous habit of this genus shows its close affi- 

 nity with Casseheera on the one hand, and with Adiantnm on 

 the other, differing from the first by its broad sorus, and 

 from Adiantum chiefly by the compound receptacle of Pla- 

 tyloma not being so much altered in texture and reflexed as 

 the venose receptacle or indusium oi Adiantum, and although 

 there is little or no affinity in habit between this genus and 

 AUosorus, yet the character of the sori is analogous. 



54. Adiantum, Linn. J. Sm. 



Coste excen trie or wanting; rem unilateral or radiating, 

 forked ; venules direct, their apices terminating in the axis of 

 the indusium, which is venose and sporangiferous on its 

 under side, at length replicate, constituting round, reniform, 

 oblong or linear continuous marginal sori. 



Fronds varying from simple reniform to decompound. Stipes 



