6 FLORA. 



cally. Indusia fixed by their broad bases to short oblique veinlets. [Greek, in al- 

 lusion to the flexible stipes. 1 About 20 species, mostly tropical. 



i. Lygodium palmatum (Bernh.) Sw. CLIMBING FERN. HARTFORD FERN. 

 (I. F. f. 13.) Rootstock slender, creeping. Stipes slender, flexible and twining; 

 leaves 4-10 dm. long, their short alternate branches 2-forked, each fork bearing a 

 nearly orbicular 4-7-lobed pinnule which is more or less cordate at the base with 

 a narrow sinus ; surfaces naked ; fertile pinnules contracted, several times forked, 

 forming a terminal panicle ; sporanges solitary, each covered by a scale-like in- 

 dusium. In moist thickets and open woods, N. H. and Mass, to Penn., Fla. and 

 Term. ; rare. Summer. 



Family 5. POLYPODIACEAE R. Br. 



Fern Family. 



Ferns of various habit, the rootstocks horizontal and often elongate, 

 or short and erect, the leaves entire, pinnate, pinnatifid or decompound, 

 coiled in vernation. Sporanges borne in clusters (sori) on the lower side 

 or margins of the leaves or their segments, stalked, provided with a ver- 

 tical ring, opening transversely. Sori with or without a membranous 

 covering (indusium). Prothallium green. About 200 genera and 3000 

 species of wide distribution. 



Leaves all flat, or their edges only slightly revolute. 

 Sori without indusia. 



Sori roundish or not more than twice as long as broad. 



Stipes articulated to the rootstocks ; leaves in our species pinnatifid. 



i. Poly podium. 

 Stipes not articulated to the rootstocks ; leaves in our species 2-3-pinnatifid 



or ternate. 14. Phegopteris. 



Sori linear and marginal. 2. Notholaena. 



Sori with marginal indusia formed of the more or less altered edge of the leaf. 

 Sporanges at the ends of veins, borne on a reflexed portion of the leaf. 



3. Adiantum. 

 Sporanges borne on a continuous vein-like receptacle which connects the apices 



of the veins. 4. Pteridium. 



Sporanges at or near the ends of unconnected veins. 



Leaves of two forms ; stipes pale. 5. Cryptogramma. 



Leaves uniform ; stipes usually dark-colored. 



Sori mostly forming a continuous indusium around the segment. 



6. Pellaea. 



Sori minute ; indusium usually interrupted, if continuous the seg- 

 ments small and bead-like. 7. Chetlanthes. 

 Sori dorsal or marginal, provided with special indusia. 



Sori linear or oblong ; indusia more than twice as long as broad. 

 Sori in chain-like rows parallel to the midribs or rachises. 



8. Woodwardia. 

 Sori all oblique to the midrib or rachises ; veins free. 



Sori single on the upper side of a veinlet or rarely crossing it. 



9. Asplenium. 

 Sori confluent in pairs with an apparently double indusium opening in 



the middle ; leaf simple. 10. Phyllitis. 



Sori partly parallel to the midrib, partly oblique ; veins united. 



ii. Camptosonts. 



Sori roundish, indusia less than twice as long as broad. 

 Indusium superior. 



Indusium orbicular, peltate, fixed by the centre. 12. Polystichuin. 



Indusium reniform or orbicular with a narrow sinus by which it is 



attached to the leaf. 13. Dryopteris. 



Indusium delicate, partly inferior, fixed by a broad base and enclosing the 



sorus like a hood. 15. Filix. 



Indusium wholly inferior. 



Indusium roundish or stellate. 16. Woodsia. 



Indusium cup-shaped or somewhat 2-valved. 17. Dennstaedtta. 



Spore-bearing leaves closely rolled together with necklace-like segments. 



Leaves with free veins ; rootstock stout, erect. 18. Mateuccia. 



Leaves with anastomosing veins ; rootstock creeping with scattered leaves. 



19. Onoclea, 



