ASFLENIUM. 



FILICES. 



493 



Subgenus Athyrium, Roth. Fronds bi-tripinnatifid : ultimate segments toothed or deeply 

 laciniate. Sori short, sometimes double, mostly seated on the middle or lower part of 

 the venules. Involucre vaulted ; the extremities free. 



5. Asplenium thelypterioides, Michx. Silvery Spleenwort. 



Frond pinnate ; the pinnae linear-lanceolate, deeply pinnatifid ; segments oblong, obtuse, 

 denticulate-serrate ; sori linear-oblong, nearly straight, in approximated parallel lines. — 

 Michx. fl. 2. p. 265 ; Pursh, fl. 2. p. 667 ; Bigel. fl. Bost. p. 393 ; Torr. compend. p. 

 383 ; Beck, bot. p. 453 ; Darlingt. fl. Cest. p. 581. Diplazium thelypterioides, Presl. 



A smooth fern, 1^-2 feet high. Stipe light brown. Frond oblong-lanceolate, glaucous 

 green ; the pinna? numerous, alternate and sessile, pinnatifid nearly to the partial rachis : 

 segments 4-6 lines long ; the veins forked or simple. Sori usually arising only from the 

 upper side of the veins near the base, but sometimes also the lower side, when the sori are 

 double and applied back to back, as are likewise the involucres. There are from 10 to 14 

 sori on each segment, arranged obliquely on both sides of the midrib, forming a double row, 

 finally almost confluent. The involucre is vaulted, and of a firm texture, and of a whitish 

 or almost silvery color when young. 



Moist rocky woods, commonly in shady places : frequent. F r. July. In some specimens 

 a large proportion of the sori are double, in which state the plant was probably examined by 

 Presl, who referred it to Diplazium. 



6. Asplenium Filix-fcemina, R. Br. Female-fern. 

 Frond bipinnate ; pinnules varying from oblong to linear-lanceolate ; segments oblong- 

 lanceolate, incisely and rather obtusely serrate, the serratures toothed ; sori oblong, at first 

 nearly straight, finally lunate and recurved. — R. Br. prodr. p. 150; Spreng. syst. 4. p. . . ; 

 Hook. Brit. fl. (ed. 3.) p. 453 ; J. Smith, I. c. A. Athyrium, Schk. Fil. t. 78 (ex Hook.) ; 

 Spreng. I. c. A. Michauxii, Spreng. I. c. Aspidium Filix-fcemina, Swartz ; Eng. bot. t. 

 1459 ; Willd. sp. 5. p. 276 ; Pursh, fl. 2. p. 664 ; Beck, bot. p. 455. A. asplenioides, 

 Swartz ; Willd. I. c. ; Pursh, I. c; Torr. compend. p. 382 ; Beck, I. c. ; Darlingt. fl. Cest. 

 p. 579. A. angustum, Willd. I. c. ; Pursh, I. c. Nephrodium asplenioides & Filix-fcemina, 

 Michx. fl. 2. p. 268, Athyrium Filix-fcemina, Roth.; Hook. fl. Bor.-Am. 2. p. 262. 



Whole plant smooth, 1 \ - 2§ feet high. Stipe tawny. Outline of the frond varying from 

 oblong to lanceolate : pinnae 2-5 inches long, acuminate : segments 4-6 lines long, 

 decurrent at the base on the secondary rachis, doubly dentate-serrate. Sori 10 - 16 on each 

 segment, with sometimes an additional sorus on the lowest tooth of the upper side, one 

 corresponding to each tooth, and seated on the upper side of the lowest veinlet or that which 

 leads to the sinus, near the midrib ; at first linear-oblong, but becoming recurved by the 

 growth of the capsules, so that the back of the involucre is sometimes doubled upon itself. 

 Involucre membranaceous, somewhat vaulted ; the upper extremity free. 



