Aspidium. 91 



^^^Fronds bipinnate or tripinnatifid ; seg^ments spinulose-toothed. 



14. A. rigidum, Swz., var. argutum, D. C. Eaton. Rhizoma 

 short, stout ; fronds in a crown on chaffy stalks, half-evergreen, 

 smooth above, paler and more or less glandular beneath, 1° — 3° 

 high, ovate-lanceolate or triangular-lanceolate, bipinnate ; pinnas 

 broadly oblong-lanceolate, the lowest ones broadest scarcely 

 shorter than the middle ones ; pinnules oblong, incised or doubly 

 serrate with spinulose teeth ; indusia firm, convex, the edge bear- 

 ing short-stalked glands. [A. argutum, Kf.) Cal., Ore. IV. 



15. A. spinulosum, Swz. Stipes with a few, pale-brown, de- 

 ciduous scales ; fronds ovate-lanceolate, bipinnate, the pinnae ob- 

 lique to the rachis, elongated triangular, the lower pairs broadly 

 triangular; pinnules oblique to the midrib, connected by a very 

 narrow wing, oblong, incised or pinnatifid with lobes spinulose 

 toothed ; indusia smooth without marginal glands. N. Y. and N. 

 Eng. II. 



Var. dilatatum, Horneman, Scales of the stipes large, brown 

 with a darker centre ; fronds broadly ovate or triangular-ovate, 

 oftenest tripinnate ; pinnules lance-oblong the lowest often much 

 elongated ; indusium smooth and naked. N. Eng. to Ore. and 

 northward.. II. 



Var. intermedium, D. C. Eaton. Scales of the stipes few, 

 brown with a darker centre ; fronds oblong-ovate, bi — tripinnate ; 

 pinnae spreading oblong-lanceolate, the lowest unequally trian- 

 gular-ovate ; pinnules crowded, pinnately divided ; margin of in- 

 dusium denticulate and beset with stalked glands. Northern 

 U. S. II. 



16. A. Boottii, Tuckerman. Scales of the stipes pale brown ; 

 fronds elongated oblong or elongated lanceolate in outline ; pin- 

 nules broadly oblong, very obtuse, the lower pinnatifid, the upper 

 and smaller merely serrate ; indusia minutely glandular. [A. 

 spinulosum, var. Boottii, Gray.) N. Eng., N. Y. and northward. II. 



I 2. POLYSTICHUM, Roth. Indusium orbicular and entire, 



peltate, fixed by the depressed centre; pinnez and pinnules usually 



auricled on the upper side at base, mucronately serrate; veins free. 



^Fronds simply pinnate. 



'\ Fronds long-stalked, lanceolate. 



17. A. acrostichoides,* Swz. (Christmas-fern). Stipes 6' 

 — 8' long, densely clothed below with pale brown lanceolate scales ; 

 fronds X° — 1° high; 3' — 5' broad ; pinnse linear-lanceolate some- 

 what falcate, half-halberd shaped at the base, serrulate with ap- 

 pressed bristly teeth ; the fertile ones contracted and smaller, bear- 



