464 STRUTHIOPTERIS. 



At top it divides equally into 2 compound branches, each of which gives off. 

 at reo'ular intervals, G— 8 simply pinnate leaflets i'roni the outer side, giving 

 the whole irond the form of the crescent. Ultimate sejrnicnts dimidiate, the 

 lower margin being- bounded by the midrib and the veinlets all unilateral. Jl. 



8. D 1 C K S O' N I A . 

 Sori mirf;;inal, roundish, distinct; indusium double, one 

 superficial, opening outwards, the other marginal and opening 

 inwards. 



D. piLosiu'scuLA. Fine-haired Mountain Fern. 



Frond bipinnate; ?eff/Zft/5 lanceolate, sessile ; segments pinnatifid, dccirrcnt, 

 oblong-ovate, ultimate segments toothed ; siZ/^e a little hairy. A large and 

 delicate fern, in pastures, roadsides, among rocks and stones. Fronds 2 — 3 

 feet hiiih, in tufts, and remarkable for their numerous divisions and subdivis- 

 ions. Stipe and rachis smooth, with tlie exception of a few soft, scattered 

 h-iirs. Leaflets alternate, approximate ; segments deeply divided into 4-tooliicd 

 ultimate segments. Sori minute, solitary, on the uj)pcr margin of the seg 

 ments. July. 



9 . O N O C L E' A . 



Thecaa coveriFig (he whole lower surface of the frond ; 

 indusia formed of the segments of the frond, whose margins 

 are revohite and contracted into the form of a bcrrj, opening, 

 but not expanding. 



O. sensi'bilis. Sensitive Firn. 



Sterile fronds pinnate; leaflets lanceolate, acute, laciniate, the upper ones 

 vmited ; fertile fronds bipinnate, with recurved and globular, contracted 

 seo'mcnts. Common in low grounds. Fronds about a foot high, the barren 

 ones broad and somewhat triangular in outline, composed of broad, oblong, 

 sinuate divisions the upper ones smaller, nearly entire, becoming united at 

 base. The fertile frond is very dissimilar in its form to the others, resembling 

 a compound spike, enclosing tiie fruit in the globukr segments of its shorS 

 divisions. Color dark brown. July. 



10. STRUTIIIO'PTERIS. 



Thecm dcnsel}' covering the bock of the frpnd; indusia 

 seal}', marginal, o])ening internally. 



S. Germa'nic.v. IVilld. Ostrich Fern. S. Pennsylvanica. JViUd. 



S.'eri'e fronds pinnate ; leaflets pinnatifid, sessile ; segments entire, rather 

 acute, tlie lower ones somewhat elongated. A fern of noble size and appear- 

 ance, growing in low woods and swan)ps. The steriloAfronds are often 5 orG 

 feet high, commonly about ri, numerous, in circular clumps. Stipes smooth, 

 cliannekd ; leaflets ])innatifid, with numerous segments, the lower of which 

 tire the more narrow and acute, all more or less connected at base. Fertile 

 fronds few, in the midst of the sterile, much smaller, the leaflets with numer- 

 ous!, brownish, contracted segments, densely covered by the fruit beneath. Aug. 



