CHARACTERS OF TRIBES AND GENEBA. 201 



Although they agree in general habit they have never- 

 theless been arranged by different authors under no less 

 than at least six genera, the technical characters being 

 chiefly derived from slight differences in the venation and 

 position of the sori for instance, Sagenia is characterised 

 by Presl as having no free veinlets, but I find that that 

 character is not constant, for in different specimens of the 

 same species some have the venation of Sagenia, and others 

 have free veinlets as in Aspidium, and sometimes the two 

 forms are found on the same frond ; the characters of the 

 other genera of authors are also, I consider, untenable. 

 I therefore retain them under Aspidium. 



It often happens that the indusium is soon deciduous, 

 and therefore when absent this genus cannot be distin- 

 guished from D-ictyopteris and Dryomenes ; also in some 

 species, as for instance the well-known Aspidium macro- 

 phyllum, the indusium is as often reniform as peltate. This 

 difference has led the author of the " Synopsis Filicum " 

 to consider the reniform as the normal form, and accord- 

 ingly places A. macrophyllum and other allied species 

 in the genus Neplirodium, from which they differ entirely 

 in habit. 



In the " Gartenflora," 1866, page 335, Dr. Regel had 

 characterised a new genus under the name of Gramma- 

 tosorus, which is accompanied by a figure. It, however, 

 appears to me to be founded on what may be termed an 

 amorphous form of the sori of Aspidium alatum of Wallich, 

 a large-growing Indian species, bearing numerous irregular 

 small sori, which in specimens from Malacca are irregular 

 and confluent, forming linear transverse sori analogous to 

 Menisciwn, while others on the same segment form linear 

 sori parallel with the primary veins. The same variableness 

 n the form of the sori is also to be found in A. irreguum 



