mvi. GENEEA OP FEEN8 : 



Fronds simple, coriaceo-membranaceous, the fertile narrower. 

 Rhizome short, thick, erect. This genus, though distinct in 

 aspect, presents no technical difference of generic value to dis- 

 tinguish it from Lindsaa, except the compound reticulation, and 

 free included branches of its veins, are admitted to be differences 

 thus important. Hence we regard the fact of such a genus being 

 proposed, and admitted, as entirely sanctioning the derivation of 

 generic characters from the venation of ferns. 



Ex. : D. panamense, Hook. 



(a) Veins free. 

 42. ADIANTUM. Linnceus, Gen. PL 782. 



ADIANTELLUM, Presl; APOTOMIA, Fee ; STNBCHIA F&e; MBSOPLJTOBIA, 

 Moore MS. ; SCOLOPKNDEII sp., Adamon; PIBEIDIS sp., Auct. 



Son indusiate, transverse marginal, reniform oblong or 

 linear, continuous or interrupted ; the receptacles seated on the 

 under surface of the indusium, and proceeding from the apices 

 of two or more converging venules. Indusium (inverted mem- 

 branaceous marginal lobe) venulose, sporangiferous beneath on 

 the venules ; the receptasles, therefore, resupinate. Veins flabel- 

 lately forked, or forked from a medial costa, the furcations 

 repeated; venules parallel, free, continued in the fertile parts 

 into the induaium. 



Fronds coriaceous or herbaceous, simple, pinnately or pedately 

 divided, or supradecompound ; pinnse often articulated, usually 

 dimidiate with the costa wanting. Stipes and rachis ebeneous. 

 Rhizome tufted, or short creeping. A perfectly natural genus. 

 Mesoplewna. Costa medial ; sori linear, elongate, continuous. 



Ex.: A. Wilsoni, Hook. 

 A. PhyllitidiB, J. 8m. 



A. obliquum, Willd. 

 A. lucidum, Sw. 



Synechia. Costa wanting; sori elongate, continuous. 



Ex. : A. incisum, Pr. I A. villosum, Lin. 



A. pulverulentum, Lin. \ A. varium, H. S. 1. 



Adiantellum. Costa wanting ; sori round or oblong. 



Ex.: A. reniforme, Lin. I A. Capillus-veneris, Liu. 



A. lunulatum, Etvrm. A. trapeziforme, Lin. 



A. prionophyllum, H. S. K. A. concinnum, H. S. JC, 



