590 FILICES. (FERNS.) 



1. P. Y ill tf fire, L. Fronds oblong in outline, green both sides (6'- 10 

 high) ; the divisions linear-oblong, obtuse, minutely and obscurely toothed. 

 Rocks; common. July. (Eu.) 



# * Fronds twice pinnatijid, triangular, membranaceom, annual : fruit-dots minute. 



2. P. PilCg6ptCI'iS, L. Stalk somewhat chaffy and doicny ; frond nar- 

 rowly triangular in outline, longer than broad (3' -6' long), hairy on the veins; 

 pinna; linear-lanceolate, closely approximated, the lowest pair do-flexed and 

 standing forwards; their divisions linear-oblong, obtuse, entire, each bearing 

 about 4 fruit-dots towards the base and near the margin. (P. connectilc, Michx.) 

 Damp woods; common northward. July. (Eu.) 



3. P. licxagronopterum, Michx. Stalk smooth ; frond broadly trian- 

 gular, the base (7' -12' broad) usually exceeding the length; pinnae rather distant, 

 the lower of the lanceolate obtuse divisions toothed, decurrent and forming a 

 conspicuous wing to the rhachis. Rather open woods; common, especially 

 southward. Smoother and larger than the last. 



# # # Fronds membranaceous, ternate, the primary divisions mostly twice pinnate. 



4. P. Dryopteris, L. Stalk slender and brittle, smooth ; frond smooth 

 (pale light-green, 4' -6' wide) ; the 3 principal divisions widely spreading; lobes 

 oblong, obtuse, nearly entire; fruit-dots marginal, finally contiguous. Var. 

 CALCA.REUM (P. calcareum, Smith) is more rigid, and minutely glandular-mealy 

 on the rhachis and midribs. Rocky woods; common northward. July. (Eu.) 



$ 2. MARGINARIA, Bory. Veins reticulated, forming mostly 6-sided meshes 

 around the free veinlets which bear the fruit-dots : stalks and back of the thick or 

 coriaceous frond beset with firm scurfy chaffy scales. (This is probably a distinct 

 genus ; but in our species the veins are so hidden in the coriaceous frond, that 

 they can seldom be seen at all.) 



5. P. incanum, Willd. Fronds oblong, 2' -6' long from extensively 

 creeping firm rootstocks, grayish and very scurfy underneath with thick peltate 

 scurfy scales, almost concealing the fruit-dots, which are borne on the margins 

 of the broadly linear entire lobes. Rocks and trunks of trees, Virginia and 

 Ohio to Illinois, and southward. 



2. STRUTIIIOPTERIS, Willd. OSTRICH-FERN. (Tab. 9.) 



Fruit-dots round, on the pinna} of a separate contracted and rigid frond, the 

 margins of which are rolled backward so as to form a somewhat necklace-shaped 

 body enclosing the fruit : there are 3-5 pinnate free veinlets from each primary 

 vein, each bearing a fruit-dot on its middle : the fruit-dots are so numerous and 

 crowded that they appear to cover the whole inside. Sterile fronds largo 

 (2 -3 high), very much exceeding the fertile, pinnate, the many pinna? deeply 

 pinnatifid, all growing in a close circular tuft from thick and scaly matted 

 rootstocks. Stalks stout, angular. Pinnate veins free and simple. (Name 

 compounded of orpou^os, an ostrich, and vrepls, a fern, from the plume-like 

 arrangement of the divisions of the fertile frond.) 



1. S. Grmiiilica, Willd. (S. Pcnnsylvanica, WilhL) Alluvial soil; 

 not rare northward. Aug. Fronds of this in a curious abnormal state, inter- 



