FILICES. 397 



tawny membranaceous chaff, especially at base. Son medium size, one at each 

 notch in the lobes of the upper pinnae, the lower ones being mostly sterile ; 

 induiium orbicular- reniform. 

 Huh. Rocky woodlands : frequent. Fr. July. 



520. POLiYS'TICHUM, Roth. 



[Gr. Poly, many, and StMtos, a row, or line; the sori sometimes in close lines.] 

 So-ri round, borne on the back of pinnately-forked veins. Indusium 

 orbicular, umbilicate (i. e. fixed by the depressed centre), opening 

 all round the margin. Fronds subcoriaceous and evergeen, simply, 

 or bi- tri-pinnate ; pinnae auricled at base, on the upper edge ; stipe 

 chaffy. 



1. P. aCFOSticllOides, Schott. Fronds lance oblong, simply 

 pinnate ; pinnae lance-linear, sub-falcate, bristly-cuspidate ; sori 

 finally confluent. 

 Aspidiuin acrostichoides. Willd. $ FL Cestr. ed. 2. p. 576. 



ACROSTICHUM-LIKE POLYSTICHUM. 



Fronds 9 to 18 inches long, and 2 to 4 inches wide; pinnae 1 to 2 inches long, 

 alternate, finely serrate, the serratures bristly-mucronate ; rachig clothed with 

 lance-linear chaff ; stipe 2 to 5 inches long, chaffy. Sori in a single, or more com- 

 monly in a double row, near the midrib of the smaller pinnae toward the summit 

 of the frond, at first distinct. 

 2Iab. Rocky woodlands : common. Fr. July. 



b. Yeins of the sterile frond finely reticulated. 



521. OSTOCLE'A, L. 



[An ancient Greek name; applied to this genus.] 



Fertile frond bipinnate, much contracted, the pinnules short and 

 revolute, usually rolled up into closed berry-like involucres filled 

 with sporanges, and forming a one-sided spike, or raceme. Sori one 

 on the middle of each simple primary vein, round, soon all confluent. 

 Indusium very thin, hood-like, lateral, fixed by its lower side, free 

 on the upper (i. e. toward the apex of the pinnule). Sterile frond 

 rising separately, pinnate. 



1. O. sensibiliS, L. Sterile fronds oblong- triangular ; pinnae 

 lanceolate, the lower ones distinct, pinnatifid-dentate, the upper 

 confluent, repand-dentate, or entire. 

 SENSITIVE OXOCLEA. 



Sterile froruls 6 to 15 inches long, and 5 to 12 inches wide at base ; lower pinnae 



3 to 6 inches long ; stipe 6 to 10 inches long, slender, angular, naked. Fertile fronds 



4 to 8 or 10 inches long; pinnae 1 to 3 inches long, nearly erect; pinnules triangu- 

 lar-globose, smoothish, dark brown, resembling berries in 2-rowed unilateral spikes ; 

 stipes 8 to 12 inches long, rather stout, terete, naked. 



Hob. Moist woodlands : frequent. Fr. July. 



SUBORDER II. OSMUNDIN'EAE. 



Sporanges variously collected, destitute of any proper ring, cellular-reticulated, 

 opening length-wise by a regular slit, sometimes striate-rayed on the top. 



522. OSBHWDA, L. 



[A name supposed to be of Celtic origin.] 



Sporanges globose, stipitate, naked, entirely covering the fertile 



