264 CONTRIBUTIONS FROM THE NATIONAL HEKBAEIUM. 



2. Botrychiuin virginianum europaeum Angstr. Grapeferx. Rare; in wooded 

 swamps or in deep moist woods at low altitudes; abundant in an open mossy bog 

 below Lake McDennott. The species widely distributed in N. Amer.; also in tropi- 

 cal Amer. and in the Old World. — Plants 10 to 50 cm. high; sterile blade broadly 

 triangular. 



In woods the leaves are deep green, but in the open they are yellowish green. 

 The plants vary greatly in size. Only a few isolated individuals were found by the 

 writer about Lake McDermott, except in one bog, where in the thick moss under 

 scrub birches there were hundreds of plants. 



3. BotrycMum silailolium Presl. Leathery grapefern. Rare; in a wet thicket 

 below Lake McDermott, and in sphagnum bog at Johns Lake. Alaska to Calif, and 

 Mont.; Wis. to Ont., Que., and Pa. — Plants 10 to 50 cm. high; sterile blade broadly 

 triangular, thick and hea\'ys dark green. 



The sterile blades persist for one or two years, and the species may be recognized 

 easily by this fact. 



2. POLYPODIACEAE. Polypody Family. 



Plants consisting of a rhizome and leaves, the leaves coiled in bud ; leaves simple, 

 or compound and composed of leaflet-like pinnae; sporangia borne on the lower 

 surfaces or along the margins of the leaves in clusters (sori); sori naked or with a 

 special covering (indusium). 



Leaves deeply lobed, the lobes entire. Sori dotlike, on the lower surface of the leaf. 



1. POLYPODroM. 

 Leaves compound, composed of few or numerous pinnae. 

 Sori borne along the margin of the leaf and protected at first by the inrolled margin. 



Sori distinct; leaf stalk divided above into 2 branches 2. ADIANTTJM. 



Sori not distinct, forming a continuous line about the margin; leaf stalk not 

 2-b ranched. 



Leaves large, 20 to CO cm. wide or larger, solitary 3. PTERIDITJM. 



Leaves small, usually less than 10 cm. wide, commonly tufted. 



Leaf stalks green or pale brown 4. CRYPTO GRAMMA. 



Leaf stalks dark brown or nearly black 6. CHEILANTHES. 



Sori borne on the lower side of the leaf, not at the margin. 

 Sori linear or oblong, straight or curved. 

 Leaves small, 4 to 15 cm. long, once pinnate; sori straight . . 6. ASPLENIXTM. 

 Leaves large, 25 to 100 cm. long or even larger, 2 or 3 times pinnate; sori curved. 



7. ATHYRroM. 

 Sori rounded and dotlike. 

 Indusiiun attached by the middle beneath the sori or at one side. 

 Indusium attached by the middle, split into lobes; leaves with minute 



stalked glands 10. WOODSIA. 



Indusiiun attached by one side, not lobed; leaves without glands. 



11. FIUX. 

 Indusium attached by the middle or by one side and spreading above the 

 sorus, or the indusium sometimes wanting. 

 Indusium wanting. 

 Leaves much longer than broad, in dense clumps, from a very thick 



rootstock 7. ATHYRIUM. 



Leaves about as broad as long, arising singly from a slender creeping 



rootstock 9. DRYOPTERIS. 



Indusium present. 



