194 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Rich, moist woods, particiiliirly nloii^^ brooks; rrcfjuciit, cxc-cpt on 
the plateau. 
A. angustifolium (Mielix.) Milde. Nakkow-leav?:d Spleen- 
wort. — (Asplenium -pycnocarpon 111. Fl. ed. 2). 
Rich woods, generally in alluvial pockets spread by brooks at the 
bases of rich slopes, often with Thclypieris Goldiana; occasional in the 
valley. Willianistown (Churchill) ; Adams (Schweinfurth); Cheshire 
(Winslow); Pittsfleld; 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-fcmina (L.) Bernh. have been lately treated as including two 
species and several varieties {vid. Butters, Rhodora, 19: 181 seq., 1917). 
Athyrium angustum (Willd.) Presl. is apparently the only species in 
this group that occurs in Berkshire County. It differs from Athyrium 
asplenioidcs (Michx.) Desv., which is found in 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 io 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. 
b. 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, f. 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 sterile fronds oblong-lanceolate, 
strongly toothed or pinnatifid, somewhat acute. 
A. angustum, var. eJatius. 
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 Fern. — {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. 
