FILTCES. (TRUE FERNS.) 443 



«- •*- Fronds more than once pinnate or pinnatifd. 



3. A. septentrionale, Hoffm. Fronds 3 to 6 inches high, subcoria- 

 ceous, the stalk alternately forked ; branches widening into a few (2 to 5) very 

 narrowly cuneate and acuminate entire or sparingly toothed segments : veins 

 closely parallel and forking : sori elongated, 1 to 3 to a segment. — Colorado 

 and New Mexico. In crevices of rocks. 



* * Indusia variously curved, often crossing the fertile veinlet and continued a 

 short distance down the other side of it. 



4. A. Filix-fOBmina, Bernh. Fronds 1 to 3 feet long, softly membra- 

 naceous, oblong-lanceolate, 2 to 3-pinnate ; pinnules adnate to the secondary 

 rhachis, ovate to elongated-lanceolate, variously toothed or incised : indusia 

 lacerate-ciliate. — Common almost everywhere. 



9. PHEGOPTERIS, F&. 



Sori on the back of the veins below their attenuated apices. Differs from 

 Aspidium only in having no indusium. In our species the fronds are trian- 

 gular, ternate, the primary divisions stalked, and the rhachis is not winged. 



1. P. Dryopteris, Fee. Fronds smooth and thin, 4 to 10 inches wide and 

 long; lateral divisions divergent; all triangular and pinnate, the pinnae pin- 

 natifid into oblong, obtuse, entire or even pinnately lobed segments ; lowest 

 inferior pinna of the lateral divisions equal to the second pinna of the middle di- 

 vision. — From the mountains of Colorado to Oregon, eastward through the 

 Northern United States, and far northward. Open rocky woods. 



2. P. calearea, Fee. Fronds minutely glandular and somewhat rigid, 4 to 

 8 inches wide and long ; lateral divisions ascending ; all triangular and pinnate, 

 the pinnae pinnatifid into oblong obtuse or even pinnately-lobed segments; 

 lowest inferior pinna of the lateral divisions equal to the third pinna of the middle 

 division. — Collected in Minnesota (Miss Cathcart), but, according to Professor 

 Eaton, to be expected from Lake Superior to Idaho. 



10. ASPIDIUM, Swartz. Shield Fern. Wood Febn. 



The round indusia attached to the middle of the sorus by a short central 

 stalk, or roundish-reniform and attached at the base of the sinus. 



* Indusium roundish-reniform or orbicular with a narrow sinus: in ours the fronds 

 are larger, subcoriaceous or nearly so. 

 1. A. Filix-mas, Swartz. Fronds 1 to 3 feet long, broadly oblong- 

 lanceolate, somewhat narrowed and twice pinnate towards the base ; pinnae 

 lanceolate-acuminate from a broad base ; pinnules or segments oblong to ovate 

 lanceolate, obtuse or acute, toothed or incised, not glandular but sometimes 

 slightly chaffy beneath, the upper confluent : sori near the midvein, commonly 

 only on the lower half of each segment : stalks very chaffy with large scales. 

 — Occurs generally throughout the continent, in several varieties. In Colo- 

 rado and the Dakotas the following form has been found : — 



