544. CONTRIBUTIONS FROM THE NATIONAL HERBARIUM, 
Plants very delicate, the stipe 0.1 mm. thick; 
lamina subpinnate throughout, the 
segments narrowed at the base, ob- 
acurely joined..............2.22000.. 
Scales of the rhizome freely long-ciliate....... seeee 
Veins of the fertile (and sometimes also the sterile) seg- 
ments forked; or, in nos. 9 and 15, the fertile spur 
commonly obsolete. 
Lamina nearly glabrous to pubescent, never long- 
setose with stiff reddish hairs. 
Scales of the rhizome entire; partition cell walls 
very thin, 
Leaf tissue delicate, translucent; scales 0.6 to 
1.3 mm. long..........202.0...00.0.. 
Leaf tissue coriaceous, opaque; scales mostly 
1.5 to 2 mm. long................. eee 
Scales of the rhizome whitish-ciliate; partition 
cell walls strongly dark-sclerotic. 
Sporangia long-setose. 
Fronds 4 to 8 cm. long, delicately her- 
baceous; lobes 15 to 30 pairs... .. 
Fronds 1.5 to 3.5 mm. long, spongiose- 
herbaceous; lobes 5 to 12 pairs, 
shorter, broader ................ 
Sporangia not setose. 
Fronds 2 to 5 (rarely 8) cm, long; lamina 
3 to 4 mm. broad, pinnatifid 
about three-fourths the distance to 
the rachis, the segments small, 
porrect, close, acutish...... veeeee 
Fronds 8 to 20 cm. long; lamina 4 to 9 
mm. broad, very obliquely lobed 
about half way to the rachis, the 
lobes large and rounded..... weeee 
Lamina invariably reddish-setose, the hairs usually 
very long. 
Scales of the rhizome with occasional irregular 
teeth, these 1 to 3 cells broad. 
Fertile branch of vein usually long-produced; 
segments narrow, usually subdistantin 
drying, distinctly gibbous............ 
Fertile branch of vein short or (in no. 15) 
commonly obsolete, the sorus then 
subsessile; segments broader, closer, 
never gibbous. 
Segments obliquely triangular or deltoid- 
oblong..................22220--. 
Segments oblong, rounded at the apex. 
Lamina delicately herbaceous, co- 
piously long-setose; vein of fer- 
tile segments distinctly genicu- 
late... 2... ee eee eee eee 
Lamina more or less spongiose, 
sparingly setose, the hairs 
shorter; vein of fertile segments 
arcuate, decurved.............. 
6. P. williamsii. 
7. P. caucanum, 
10. 
lL. 
13. 
14, 
16. 
. grisebachii. 
. perpusillum, 
. mitchellae. 
. shaferi. 
. schenckit, 
. organense. 
. trichomanoides, 
. serricula. 
. basiattenuatum, 
. sherringii. 
