38 ENGLISH BOTANY. 



Suborder III.— PO L YP OD I A C EiE. 



Sporangia with an incomplete vertical annulus, and opening by a 

 transverse slit on the side where the annulus is incomplete. 



Tribe I.— POLYPODIES. 



Rootstock growing in advance of the fronds, the stipes of which is 

 articulated to the rootstock, and separates from it, leaving a distinct 

 scar. Sori roundish or more or less elongated, attached to the hack 

 of the veins, without an indusium. 



This is the only tribe of British Ferns belonging to Mr. John 

 Smith's division Eremobrya, which is characterised " Fronds solitary, 

 solitary, lateral, and articulate with its caudex ;" all the following 

 tribes belong to his division Desmobrya, and have the " fronds 

 terminal, solitary, fasciculate, adherent to the caudex." (J. Smith, 

 ' Hist. Filicum,' pp. 61-79.) I agree with the late Mr. E. Xewman 

 (' Phytologist,' ser. 1, vol. v. p. 229) that such plants as Pteris aquilina, 

 which have a rhizome growing in advance of the fronds, cannot 

 naturally be referred to Desmobrya ; though I cannot go so far with 

 him as to join them with Polypodium and the other Eremobrya. 

 Probably Pteris aquilina and such Ferns as have a rhizome growing 

 in advance of the fronds, but the rachis of the fronds continuous with 

 the rhizome and not articulated to it, ought to be formed into a 

 separate division to be placed between Eremobrya and Desmobrya — 

 as natural primary divisions of the suborder Polypodiaceae. 



GENUS IV.— POLYPODIUM. Linn. 



Rootstock scaly, growing in advance of the fronds. Fronds solitary, 

 their stipes articulated to the rootstock. Veins free. Sori roundish, 

 rarely oval, terminating the lower anterior veins. Indusium absent. 



Name from -oXvs (pcius) many, and -ovs {pous) foot. 



SPECIES L-POLYPODIUM VULGARE. Una. 



Plate 1842. 



Bab. Crypt. Yasc. Europ. Exsicc. No. 1544. 



Ctenopteris vulgaris, Xeicm. Pkyt. 1851, App. p. 29 ; Brit. Ferns, ed. iii. p. 42. 



Rootstock thick, at first densely clothed with peltately attached 

 reddish-brown ovate-triangular and lanceolate acuminate or cuspidate 



