I20 OUR NATIVE FERNS AND THEIR ALLIES. 



XXIX. 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. ovoi, a vessel, and nXeieiv, to 

 close, alluding to the fertile fronds. A single species. 



I. 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 ; veins copiously anasto- 

 mosing. In var. obtusilobata Torn the sterile fronds are again 

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

 sori. New England to Florida and Kansas. 



XXX. MATTEUCCIA Todaro. 



Sori round, borne on the veins of a contracted fertile frond, 

 concealed by their revolute margins. Fronds growing in a 

 crown, dimorphous. Veins free. Name from Cailo Matteucci, 

 an Italian professor of physics. Contains two or three species. 



I. M. struthiopteris (L.) Todaro. (Ostrich-fern.) Fer- 

 tile fronds i° — ii° long, simply pinnate with necklace-shaped pin- 

 nae formed of the strongly revolute margins ; sterile fronds 2° — 6° 

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

 lowest pinnse gradually much shorter ; veins pinnate, free and 

 simple ; sori crowded, confluent. (0?ioclea struthiopteris Hoffm., 

 Struthiopteris Pennsylvanica Willd., 5. Germanica Willd., Os- 

 munda struthiopteris L.) New England to Illinois. 



XXXI. WOODSIA R. Br. 



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

 Indusium inferior, thin and 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. 



§1. EuwoODSIA. Indusium minute or evanescent, open and 



