194 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 



Rich, moist woods, particularly along brooks; frequent, except on 

 the plateau. 



A. angustifolium (Michx.) Milde. Nabeow-leaved Spleen- 

 WOET. — (Asplenium pycnocarpon 111. Fl. ed. 2). 



Rich woods, generally in alluvial pockets spread by brooks at the 

 bases of rich slopes, often with Thelypteris Goldiana; occasional in the 

 valley. Williamstown (Churchill); Adams (Schweinf urth) ; Cheshire 

 (Winslow); Pittsfield; Lenox; Stockbridge; Sheffield. On South 

 Mountain, Pittsfield, one colony grows in rich soil on a flat rock. 

 . The ferns which have passed in Massachusetts as Asplenium 

 Filix-femina (L.) Bernh. have been lately treated as including two 

 species and several varieties {vid. Butters, Rhodora, 19: 181 seq., 1917). 

 Aihyrium angustum (Willd.) Presl. is apparently the only species in 

 this group that occurs in Berkshire County. It differs from Athyrium 

 asplenioides (Michx.) Desv., which is found iii eastern Massachusetts, 

 in having the horizontal or somewhat oblique rootstock completely 

 concealed by the thick fleshy bases of the old fronds. The species and 

 two varieties may be distinguished by the following key. 



Key to Athyrium angustum and varieties. 



a. . Fronds dimorphic, the fertile coriaceous, contracted, sori at maturity 



confluent and covering the lower side of the fertile pinnules. Sun forms, 



found only in region of hot summers. 



h. Longest pinnae of the fertile frond 5-12 cm. long, pinnules 4-12 mm. 



long, simple, sori mainly asplenoid {vid. Rhodora, 19: 174, 176, 1917); 



pinnules of sterile fronds oblong-obtuse, but slightly toothed or 



lobed A. angustum, i. typicum. 



b'. Longest pinnae of fertile frond 1-2 dm. long, pinnules 12-25 mm. 

 long, pinnatifid, sori several on each of the lower segments, often 

 horseshoe-shaped; pinnules of sterilp fronds oblong-lanceolate, 

 strongly toothed or pinnatifid, somewhat acute. 



A. angustum, var. elatius. 

 a'. Fronds not dimorphic, coriaceous or contracted, sori discrete at maturity. 

 Forms of regions with cool summers, found also in dense shade in warmer 

 regions. Pinnules lanceolate, sub-acute, strongly toothed or pinna- 

 tifid, the segments toothed, membranous wing along the rhachis obscure 

 or wanting A. angustum, var. rubellum. 



A. angustum (Willd.) Presl. Lady Febn. — {Asplenium Filix- 

 femina Man. ed. 7 in part; Athyrium Filix-foemina 111. Fl. ed. 2 in 

 part; vid. Rhodora, 19: 190, 1917.) 



Dry open thickets; frequent. 



