FILICES. 119 



XXIII. ONOCLEA L. 



Sori round, borne on the back of the veins of the contracted 

 fertile frond, and quite concealed by their revolute margins. 

 Indusium very thin membranous, hemispheric or hood-like, 

 fixed at the inferior side of the sorus. Fronds conspicuously 

 dimorphous. Name from Gr. oko?, a vessel, and /cAe/e/K, to close, 

 alluding to the fertile fronds. A cold temperate genus contain- 

 ing three species. 



§1. EUONOCLEA. Veins of sterile frond copiously anasto- 

 viosing. 



1. O. sensibilis L. (Sensitive-FERN.) Fertile fronds bi- 

 pinnate, much contracted ; pinnules short, usually rolled up and 

 converted into berry-shaped closed involucres, and forming a 

 one-sided panicle; sterile fronds broadly triangular, deeply pin- 

 natifid into lanceolate-oblong pinnse, which are entire, undulate, 

 or the lowest pair sinuate pinnatifid ; veins copiously anasto- 

 mosing. In var. obttisilobaia Torr. the sterile fronds are again 

 pinnatifid, more or less contracted and revolute, and bear a few 

 sori. New England to Florida and Kansas. 



§2. Struthiopteris Willd. Veins all free. 



2. O. struthiopteris (L)Hoffni. (OSTRICH FERN.) Fertile 

 fronds 1° — i^" long, simply pinnate with necklace-sliaped pinnse 

 formed of the stiongly revolute margins; sterile fronds 1° — 6° 

 long, growing in a crown, broadly lanceolate, bipiunatifid, the 

 lowest pinnae gradually much shorter; veins pinnate, free and 

 simple; sori crowded and confluent. Sterile fronds are some- 

 times partially contracted and bear sori analogous to var. 

 obiusilobata above, (p. Gernianica Willd., O. nodidosa Michx., 

 Struthiopteris Pe7insylvanica Willd., S. Germanica Willd., 

 Osmunda struthiopteris L.) New England to Illinois. 



XXIV. WOODSIA R. Br. 



Sori round, borne on the back of simply forked free veins. 

 Indusium inferior, thin ami often evanescent, either small and 

 open, or early bursting at the top into irregular pieces or lobes. 

 Named for Joseph Woods, an English botanist. A genus of 

 high temperate or boreal latitudes including 15 species. 



§ I. Eu WOODSIA. Indiniuin minute or evanescent, open and 



