XXVI. GENEEA OF FERNS : 



Veins arcuately anastomosing at the base, forming costal areoles ; 

 venules simple or forked, parallel, connivent with the thickened 

 margin. 



Fronds rigid, opaque, pinnato-pinnatifid. Khizome arbor- 

 escent. The tree-like habit, elevated receptacle, thick indu- 

 sium, and arcuately-anastomosed basal veins, indicate a distinct 

 group, with which, however, we are but little acquainted. 



Ex, : S. cyatheoides, JE7/. I S. pallida, We. and Am. 



S. Souleytiana, Baud. \ S. squarrosa, 6faud. 



4. PLETTBOGBAMMEJB. 

 (a) Veins consisting of a costa only. 



22. MONOGEAMMA, ScTikuhr, Crypt. Gewdch. 82. 



VAGiKtnABiA, F6e ; COCHT.IDII sp., Kaulfuss ; GBAMMITIDIS sp., Auet ; 

 PTBEIDIS sp., Auct . ; PLEtrsoGEAMMATis sp., Fee; ASPLENII sp., Sa:artz ; 

 ACEOSTICHI sp.,Sivartz; T^EKITIDIS sp., Metteniug. 



Sort sub-immersed, non-indusiate, linear elongate near the 

 apex of the frond, the receptacle formed of a portion of the costa. 

 Veins reduced to the costa only. 



Fronds small graminiform or rachiform, simple or forked. 

 Ehizome creeping. Curious little plants of extreme simplicity of 

 structure. 



Monogramma.SoTi lying in a longitudinal depression of the gramini- 

 form fronds. 

 Ex. : M. graminea, Schkuhr. \ M. furcata, Dem. 



Vaginnlaria. Son occupying a vaginifonn expansion of the rachiform 



fronds. 

 Ex. : M. trichoidea, J. Sm. 



(b) Veins consisting only of a costa t and the intramarginal recep- 

 tacles parallel with it. 



23. DICLIDOPTERIS, BracJcenridge, United States Expl. 



Exped. xvi. 135, Atlas, t. 17. 



Sori immersed, non-indusiate, linear, continuous, sub-costal ; 

 the receptacle formed of a simple vein proceeding from each side 

 the costa, near its base, and running parallel with it ; sunk in a 

 deep oblique furrow open towards the costa, over which the two 



