70 A CONTRIBUTION TO, ETC. 



viently placed in two sections, the one comprising the Polypodia, 

 which have free veins, and the other, those which have veins 

 more or less anastomosing or netted. It is true that this ar- 

 rangement appears to separate some ferns agreeing in habit and 

 appearance (such for instance as . tenellum., and . Billardieri) ; 

 but on the whole it will be found most convenient for the study 

 of the genus. In the first section the species are very limited, 

 viz., P. Australe, P. tenellum, P. grammitidis, and P. rugosulum. 

 The first of these is Brown's Grammitis Australia, a small fern, 

 with simple or undivided fronds of a linear lanceolate shape, 

 seldom exceeding two or three inches in length, and growing in 

 dense p'atches 011 the sides of moist rocks. It is common in 

 many parts of Australia, and is widely distributed in other parts 

 of the world. P. tenellum is a very elegant fern with a climbing 

 habit, pinnate fronds, and the stipites jointed above the base. 

 This is the Artliropteris tcnella of Smith, the pinnae being arti- 

 culated to the rachis ; and it is mentioned by Berkeley as " a 

 most observable point," that the New Zealand species has no in- 

 dusium; "a striking proof," he remarks, "of the comparatively 

 small value of the indusium." This remark was made on the sup- 

 position that the genus Artliropteris could be maintained, and 

 that A. tenella and A. allo-punctata were very nearly allied; but 

 Sir William, takes a different view of the species, and whilst 

 he retains the one without an indusium in the genus Polypo- 

 dium, he refers the other with the reniform sori, to Nephrodium. 

 I have alluded in my introductory remarks to the difficulty of mak- 

 ing any systematic arrangement of ferns which is not open to ob- 

 jection, and certainly the case before us furnishes an instance ; 

 for it must be admitted that the ferns in question resemble each 

 other in the climbing caudex, and jointed stipites, whilst in other 

 respects they differ so materially as to render it necessary to place 

 them in different genera. P. tenellum is frequently found adhering 

 to the caudices of tree ferns, as well as on Quint inia Sieberi, Poly- 

 osma CunningJiami, and other trees which are usually seen in the 

 dark moist forests where the trap formation prevails. This 

 species occurs not only in Australia, but also in New Zealand 

 and many islands of the Pacific. P. grammitidis is generally des- 

 cribed as a Tasmanian or New Zealand plant, but Dr. Mueller 

 has found it on the South-eastern parts of Australia, and he 



