2 ADIANTUM. 



pinnatifid), variable in texture from membranaceous to co- 

 riaceous. Costa, if present, excentric, generally indistinct or 

 obsolete. Veins simple or usually forked, sometimes radi- 

 ating, rarely (in Hewardia, J. Sm.) anastomosing. Stipes 

 frequently black and glossy. Pinnules ofteti cuneated and 

 oblique. 



This Genus may be said to be a natural one, that is, generally easily re- 

 cognized, even when destitute of fructification ; the essential character, 

 however, consisting in the position of the capsules or sori upon the under- 

 side of the involucre: by that mark alone are some species with small and 

 distinct sori to be distinguished from Cheilant/ies* while others almost 

 merge into Pteris. If, however, the Genus is, as a whole, well marked, 

 great indeed is the difficulty of defining the limits of the species, or of 

 knowing what are the species of authors without the aid of faithful figures, 

 or authentically named specimens. In the several stages of growth, too, 

 some species assume totally diflferent appearances, and all kinds of shapes 

 of pinnules are seen on one and the same frond. The presence or absence 

 of fructification also changes considerably the outliue of a pinnule. I re- 

 gret, for my friend Mr. Heward's sake, that I cannot concur with those 

 who consider the anastomosing of the veins as alone sufficient to constitute 

 a genus of the Hewardia, J. Sm., and I shall be gratified if Mr. Smith 

 himself would see the matter in the same light, and distinguish some bet- 

 ter marked plant with the name of so excellent a man and so great a lover 

 and student of Ferns. Hewardia adiantoides, as will be shown, is not the 

 only Adiantum in which the veins anastomose ; and there are various de- 

 grees of union, and in plants not otherwise allied to each other; so that 

 such a character cannot be held to afford even tolerable sections : nor, 

 practically, can such characters, derived from the fructification, as those of 

 "(S'ori incequales v. liiieares, continui, vel breviores contiguV (Adianta Minervae, 

 von Martins), and " Sori aquales,glohosi, distincti. Indusium semilunatum" 

 (Adianta Veneris, von Mart.) of Presl. Such characters, distinct enough 

 in some, seem to be combined in other individuals in one and the same 

 species. In subsections they may be with some convenience employed. 



§ I. Fro7id simple. (Sp. 1—3). 



1. A. reniforme, L. ; frond reniform with a broad shallow 

 sinus, stipes slender. (Tab. LXXI. A.). — Linn. Sp. PI. 1556. 

 Willd. Sp. PL V. 427. Sw. Syn. Fil. 120. 



Hab. Madeira, Teneriffe. 



2. A. asarifolium, Willd. ; frond orbicular reniform with 

 a deep and narrow sinus the lobes generally overlapping. 

 (Tab. LXXI. B.)— Willd. Sp. PI. v. p. 427. A. reniforme, 

 Bory, Voy. i. 358. 



Hab. Mauritius, Bourbon. — I am aware that most botanists, except 

 Willdenow, consider the present plant to be identical with the previous one. 



* Ou this ground I have removed Adiantum radiatum to Cheilanthes, 

 as properly suggested by Mr. J. Smith. 



