ASPIDIUM. 



FILICES. 



497 



revolute when in fruit ; sori small, nearly medial, contiguous and finally confluent. — Swartz, 

 I. c. ; Engl. hot. t. 1018 ; Willd. sp. 5. p. 249 ; Pursh, fl. 2. p. 661 ; Bigel. fl. Bost. p. 

 390 ; Torr. compend. p. 381; Beck, hot. p. 449 ; Darlingt. fl. Cest. p. 577. Polypodium 

 Thelypteris, Linn. mant. p. 505. Lastrea Thelypteris, J. Sm. 



Stipe about a foot long, smooth and naked. Frond 10-12 inches long and 4-5 inches 

 wide, oblong-lanceolate in outline ; the pinnas mostly opposite, very numerous, pinnatifidly 

 cut into numerous small segments nearly down to the midrib, the lower ones longest : segments 

 3-4 lines long, varying from rather acute to obtuse ; the margin obscurely crenulate or 

 entire, finally revolute, smooth above, a little hairy underneath : veins mostly simple, some- 

 times forked. Sori situated rather below the middle of the veins, between the margin and 

 the midrib. Involucres orbicular-reniform. 



Swamps and wet thickets : frequent. Fr. July. A common European species. 



6. Aspidium Noveboracense, Willd. New-York Shield-fern. 



Frond pinnate ; the pinnae linear-lanceolate, sessile, the lowest ones gradually smaller and 

 usually deflexed, deeply pinnatifid ; the segments oblong, obtuse, entire, flat, ciliate ; sori 

 minute, nearly marginal, distinct. — Willd. sp. 5. p. 248 ; Pursh, fl. 2. p. 661 ; Bigel. fl. 

 Bost. p. 390 ; Torr. compend. p. 381 ; Beck, hot. p. 449 ; Darlingt. fl. Cest. p. 577. A. 

 thelypterioides, Swartz, Fil. p. 57. Polypodium Noveboracense, Linn. sp. 2. p. 1091. 

 Nephrodium thelypterioides, Michx. fl. 2. p. 267. Lastrea Noveboracense, Sm. 



About as large as the preceding species ; the stipe and rachis smooth or a little pubescent. 

 Frond of a thin and delicate texture, pale green and dull : several of the lowest pinnae 

 gradually diminishing in size downward : veins of the segments always simple, bearing the 

 sori a short distance from the margin. Involucre orbicular-reniform. 



Moist woods and thickets : common : often sterile. Fr. July. This species is certainly 

 very closely allied to A. Thelypteris, and is considered identical with it by Hooker. If the 

 characters given above prove to be constant, they must be distinct ; but I suspect that inter- 

 mediate forms sometimes occur. 



7. Aspidium acrostichoides, Swartz. Terminal Shield-fern. 

 Frond pinnate ; segments linear-lanceolate, nearly sessile, acute, somewhat falcate, mucro- 



nate-serrulate, auriculate at the base on the upper side, the upper ones smaller and fertile ; 

 sori finally confluent ; stipe and rachis chaffy. — Swartz, I. c. ; Willd. sp. 5. p. 225 ; Pursh, 

 fl. 2. p. 661 ; Bigel. fl. Bost. p. 389 ; Torr. compend. p. 381 ; Beck, hot. p. 448 ; Darlingt. 

 fl. Cest. p. 576. Nephrodium acrostichoides, Michx. fl. 2. p. 267. Polystichum acrosti- 

 choides, J. Sm. 



var. incisum : segments unequally and incisely toothed ; sori mostly distinct. — Gray, in 

 ann. lyc. N.-York, 3. p. 238. A. Schweinitzii, Beck, I. c. 

 [Flora — Vol. 2.] 63 



