CLASSIFICATION OF FERNS . 
15 
*4 
*5 
r Segments narrow-lanceolate, rather thick, attached to the stalk 
by a broad base, and confluent. Sori golden-yellow, without 
any indusium .. .. Polypodium vUlgare. 
Segments distinct or stalked, ovate-falcate, prickly-toothed, with 
a prominent angle or lobe at the base on the inner side. Sori 
with a small circular indusium .. Aspidium Lonchitis. 
Segments small, obovate. Stalk black and slender. Indusium 
attached laterally. Asplenium Trichomanes. 
Lower pair of pinnas much larger than the others, giving the 
frond a broadly triangular or rhomboidal form .. .. 16 
Lowest pair, or several lower pairs of pinnas, decreasing in size, 
or not larger than the rest. Frond ovate or lanceolate in 
\ outline .. .. .. 17 
/ Fronds once-pinnate, with pinnatifid segments. ' 
Polypodium Phegopteris. 
( Fronds twice-pinnate, the pinnas mostly opposite. 
I Polypodium Dryopteris. 
Fronds twice-pinnate, the pinnas mostly alternate. 
V Cystopteris. 
''Fronds delicate, seldom a foot high, without any brown scarious 
scales (or very few at the base of the stalk), twice-pinnate, 
with stalked pinnas . .. 18 
17 c Fronds stiff, 1 to 3 feet high or more (except in the Beech 
Polypody). The stalk more or less shaggy below the leafy 
part, with brown scarious scales (except in the Marsh Shield 
A Fern) . 19 
/ Segments with fine-pointed teeth .. Asplenium. 
I Segments oblong or lanceolate, nearly sessile, with obtuse teeth 
18 J or lobes. Cystopteris. 
j Segments small, obovate, stalked, with obtuse teeth. Delicate 
I annual. Gymnogramma. 
\ 
( Fronds pinnate, the pinnas deeply pinnatifid, the lobes entire or 
obtuse, and slightly toothed .20 
Fronds twice-pinnate, the segments sharply toothed or pinnatifid 
1 24 
1 Pinnas (all but the lowest pair) attached to the stalk by their 
broad base . Polypodium Phegopteris. 
Pinnas attached by their midrib only 
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