101 
3e Athyrium Roth. 
Finely dissected ferns with usually thin,even highly membranous, green 
fronds borne in somewhat vase-like clumps upon an often stout scaly rootcrown, 
Sori various, prevalently curving in outline, ox now horseshoe-shaped, now 
rounded, with or without an indusium, sometimes crossing to the outer or 
lower side of the fruiting veinlet,. 
6 Indusium wanting or practically so, the sporangia uncovered; 
4 sori roundish; pinnae deltoid-lanceolate le Ae americanum 
© Indusium present (often early deciduous in the lower parts but 
en near frond tip), more or less curving in outline; 
sori short-lunate; pinnae oblong-lanceolate 2. Ae filix-foemina 
1. As americanum (Butters) Maxon, Alpine Lady Fern. Ferns of strict erect 
habit, the fronds commonly somewhat folded lengthwise, light green with a 
brownish tone due to the abundant small fruit dots{visible by the upturned 269) 
blades; blades narrowly lanceolate to lance-ovate, 15-40 om, long, the pinnae 
deltoid-lanceolate, 3-5 cm. long, all rather close-set, the upper decreasing 
gradually in size to the acute frond tip, the ultimate pinnules incised and 
toothed; sori without an indusium, or indusium evanescent and very minute. 
(A. alpestre var. americanum Butters). 
Talus scree, bare rock ledges and alpine rivulets, 5800-7000 feet, rare 
with us but colonial where present. Revett Lake, Epling et al.10120; Mt, 
Pend Oreille, Christ 1213; Scurvy Mt., Kirkwood 1956, 
