Allosorus. FILICES. 487 



Stipe 1 - 3 inches long, dark brown and shining. Frond 2-3 inches long, thin and mem- 

 branaceous ; the sterile with shorter and broader segments than the fertile. Veins of the 

 sterile segments branched ; of the fertile nearly siniple, bearing at their extremities the dis- 

 tinct but approximated sori. Involucres membranaceous, broad, their free margins (in the 

 narrowest segments) extending nearly to the midrib. 



Rocks, near Whitehall {Dr. L. C. Beck) ; Yates county (Dr. SartwelV) ; and in the northern 

 part of the State : rare. Fr. July - August. In this genus the apices of the veins, instead 

 of being combined in a prominent continuous transverse receptacle, as in Pteris Aquilina, 

 are free, and bear the roundish sori, which are at first quite distinct, but finally confluent. 



•* Pterideje, J. Sm. Sori round or elongated, transverse, marginal or costal, simple or by confluence 

 compound, furnished with a special lateral involucre, the inner margin of which is free. 



4. ADIANTUM. Linn. ; J. Smith, I. c. no. 54. maidenhair. 



[From the Greek, adiantos, dry ; because the surface repels moisture.] 



Sori round, oblong, reniform or linear, marginal. Involucres formed of the reflexed and altered 

 margin of the segments of the frond, bearing the sori on the underside. — Fronds various, 

 often simple and reniform, or more or less compound : pinnae commonly oblique, truncate 

 or cuneate at the base, their petioles articulated. Veins unilateral or radiating, forked. 

 Stipe usually black and pohshed. 



1. Adiantum pedatum, Linn. Maidenhair. Mowhair. 



Frond pedate, the divisions pedate ; segments dimidiate, triangular-oblong or somewhat 

 ternate, the upper margin incisely lobed and serrate ; sori lunate. — Linn. sp. 2. p. 1095; 

 Michx. fl. 2. p. 263 ; " Schk. Fil. t. 124 ;" Pursh, fl. 2. p. 670 ; Bigel. fl. Bost. p. 395 ; 

 Torr. compend. p. 384 ; Beck, hot. p. 445 ; Darlingt. Jl. Cest. p. 583. 



Stipe smooth except near the base, blackish and shining, 8-12 inches or more in length, 

 erect, pedately branching at the summit first into 2 primary forks, and then into several 

 spreading divisions, each of which bears numerous regular alternate segments or leaflets. 

 The frond is glaucous, green, very smooth, of a thin and delicate texture. Segments on 

 short stalks, entire on the lower margin, the upper side cut into several teeth or lobes : veins 

 unilateral ; the forks terminating in the involucre, which bears the capsules on its under 

 surface. 



Shady woods : common. Fr. July. This is perhaps the most graceful and delicate of 

 North American ferns. 



