THE COMMON POLYPODY. 55 
are :一 8 Ctenopteris, and $ Phegopteris, the former with terminal sori, 
and articulated fronds, represented by Polypodium vulgare ; the latter 
with medial sori, and fronds adherent to or continuous with the 
caudex, represented by Polypodium Phegopteris. The other groups 
are :—§ Arthropteris, with terminal sori, and articulated fronds and 
pinne, represented by the Polypodium tenellum of New Zealand ; 
8 Adenophorus, with terminal sori on dilated receptacles, borne on 
costzeform i.e. simple central veins, and adherent fronds, represented 
by the Polypodium hymenophylloides of the Sandwich Islands; 
§ Prosechium, with terminal sori, and adherent fronds, represented 
by the West Indian and South American Polypodium pendulum ; 
and § Themelium, with basal sori on the costeeform veins, and adhe- 
rent fronds, as in the Polypodiwm tenuisectum of Java and Peru. 
The name of the genus is derived from the Greek polys, many, 
and pous, podos, a foot. 

SYNOPSIS OF THE SPECIES. 
$ Ctenopteris.—Sori terminal punctiform ; fronds articulated. with 
the rhizome. 
1. P. vulgare: fronds oblong or ovate, deeply pinnatifid. 
— semilacerum: lower segments pinnatifid, upper ones serrated, fertile. 
— ommilacerum; segments all pinnatifid, not narrowed below, the lobules 
pyramidal or acuminate serrate, sparingly fertile. 
— cambricum: segments all pinnatifid, narrowed below, the lobules serrated, 
crowded, barren. 
— cristatum: fronds and segments multifid-crisped at their apices. 
$ Phegopteris.—Sori medial, punetiform or sub-elongated ; fronds 
adherent to the caudex. 
* Fronds pinnate. 
2. P. Phegopteris; fronds ovate-triangular acuminate, pinnate below; pinne 
pinnatifid, the lower pair deflexed, the upper ones confluent. 
** Fronds bipinnate. 
3. P. alpestre; fronds lanceolate ; pinnules toothed, or pinnatifid ; stipes short. 
— flexile: fronds narrow, lanceolate, flaccid ; pinnc short deflexed. 
*** Fronds ternate or subternate. 
4. P. Dryopteris; fronds pentangular-deltoid, smooth ; stipes glabrous ; rachis 
deflexed. 
5. P. Robertianum; fronds erect, subternate, elongately pentangular-deltoid, 
glandular-mealy ; stipes glandular. 

