160 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Fronds relatively small, tripinnate, the primary 
pinne comprising 1 to 4 pairs of distant 
linear once-pinnate lateral branches and a 
similar elongate terminal one..............-- 
Fronds very much larger, essentially quadripin- 
nate, the secondary pinne ovate to deltoid, 
mostly imbricate, numerous, the apical ones 
gradually smaller. 
Rachises (the primary ones excepted) divari- 
cately flexuous, conspicuously spiny 
nearly throughout. 
Pinnules of the fourth order irregularly 
rhombic, consisting of 2 to 4 cuneate- 
deltoid segments, these sharply cleft 
in the middle, each lobe emarginate 
and bisoriate; spines long, acicular, 
spreading ........-...0.eee eee e eee 
Pinnules of the fourth order rhombic to 
irregularly obcordate, simple, or 
the larger ones with 1 or 2 large free 
obcordate lateral segments, the ter- 
minal segment subrhombic, irregu- 
larly 1 or 2-lobed; sori several to 
each lobe; spines short, stout, re- 
COTS... 2. eee eee eee eee eee eee 
Rachises straight; spines minute and few, 
mostly confined to the tertiary rachises. . 
Ultimate (terminal) lobes or divisions narrow, linear to 
oblong or slightly clavate (never rhombic, ovate, 
or deltoid), usually monosorous, or, if cleft at the 
apex, each portion soriferous. 
Rachises beset with long spreading acicular spines. . 
Rachises beset with conical mainly retrorse spines. 
Fronds relatively small, skeleton-like, about 
70 cm. broad; ultimate divisions almost 
capillary, 0.2 to0.5mm. broad......... 
Fronds much larger (1 to 1.4 meters broad), 
distinctly leafy in appearance; ultimate 
divisions much larger, 0.7 to 1.5 mm. 
broad; spines stouter. 
Segments of the fifth order mostly flabel- 
lately parted, sharply cuneate, the 
2 to 4 slender scarcely clavate divi- 
sions small, acutely joined; spines 
of the secondary rachis scattered, 
the larger ones 3 to 4 mm. long..... 
Segments of the fifth order once to three 
times forked (often appearing twice 
dichotomous), the 2 to 4 distinctly 
clavate divisions widely divaricate; 
spines of the secondary rachis 
numerous, short (not exceeding 1.5 
MIM.) 202s cece cece se nencnweeeneneeeee 
1. O. uncinella. 
2. O. aculeata. 
3. O. jenmanii. 
4. O. flecuosa. 
5. O. wrightiana. 
6. O. colombiana. 
7. O. fumariordes. 
8. O. gymnogrammotdes. 
