. Our native ferns and their allies; with synoptical descriptions of the American Pteridophyta north of Mexico. Ferns; Pteridophyta. FRUCrtPICATlON W F£rNS. I)? by its broad base on the inner side of the roundish sorus and partly under it. Later this is thrown back and withers away. The veins are free, and the fronds have the aspect of species of Dryopteris, but are usually more delicate in texture. 51. Onoclea.—Two quite dissimilar species have unfortu- nately been united under this name, which best form two genera Both have dimorphous fronds, the margin of the contracted fertile frond being
. Our native ferns and their allies; with synoptical descriptions of the American Pteridophyta north of Mexico. Ferns; Pteridophyta. FRUCrtPICATlON W F£rNS. I)? by its broad base on the inner side of the roundish sorus and partly under it. Later this is thrown back and withers away. The veins are free, and the fronds have the aspect of species of Dryopteris, but are usually more delicate in texture. 51. Onoclea.—Two quite dissimilar species have unfortu- nately been united under this name, which best form two genera Both have dimorphous fronds, the margin of the contracted fertile frond being strongly revolute, and concealing the fruit. Matteuccia has necklace-shaped pinnae, crowded confluent sori, and free and simple veins. Onoclea has panicled berry- shaped pinnules and copiously anastomosing veins. 52. Woodsia (Fig. 9) has round- ish sori borne on the back of the veins, with the indusia attached be- neath the sporangia and flat and open, or early bursting at the top into ir- regular lacinias or lobes. In § Eu- WOODSIA the indusia are fiat and open _, „, . ,. ^ Fig. 9. — Woodsia obtusa from an early stage, with their cleft Torr. Enlarged section of , .,. 1,1 pinnule, showing venation and ciliate margms concealed under and inferior indusia. the sori. In § Hypopeltis the indu- sium is more conspicuous and encloses the sporangium at first, but soon bursts at the top, forming several jagged lobes. 53. Dennstaedtia.—In this genus the small globular sorus is borne in an elevated, globular receptacle, and enclosed in an inferior, membranous, cup-shaped indusium. The veins are always free. The genus has been confused with tree-ferns. 54. Trichomanes (Fig. 10) has sessile sporangia borne on a filiform receptacle at the summit of a vein. The indusia are tubular or funnel- shaped, with an expanded and often somewhat two-lipped mouth. 55. Lygodlum.—In our species of climbing-fern the fructification is borne on contracted, forked pinnules „ ^ . , ^ ^ riG. 10.—
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