MAXON—STUDIES OF TROPICAL AMERICAN FERNS. 393 
slender and more or less densely covered with spreading, linear- 
subulate scales; the other, comprising the neriiformis allies, having 
the rhizomes much stouter and completely obscured by appressed, 
densely imbricate, oblong-lanceolate to lance-acuminate scales. The 
two types are very distinct and the segregation of the species com- 
posing each group is not difficult. That only one species (0. bradet) 
should have been described from America during the last 50 
years is remarkable, but perhaps attributable to lack of material. 
Even Kunze, in publishing a brief revision of the genus in 1851, 
recognized only three American species: 0. nodosa, O. pilosa, and 
O. micans, previously mentioned. Of Old World species he enum- 
erated twelve (besides three doubtful ones), most of which have since 
been reduced to O. neriiformis, though it is probable that they are 
well founded. Future collections will increase rather than decrease 
the number of American species here recognized. 
The specimens here cited are all in the U. S. National Herbarium. 
o 
KEY TO THE SPECIES. 
Rhizomes creeping, slender, squarrose-paleaceous. 
Lamina hairy, long-decurrent .........---------+---+-+-- .. 1. O. hirta, 
Lamina glabrous, cuneate at the base. 
Rhizomes pruinose, laxly and deciduously paleaceous. 2. O. bradei. 
Rhizomes brownish, densely and persistently palea- 
COOUS. 2.5. ee ee ee eee eee cece eee e eee etees 3. O. articulata, 
Rhizomes ascending or climbing, densely appressed-paleaceous. 
Phyllopodia 6 to 25 mm. long, slender, like the stipe. 
Veins 14 to 18 per centimeter; scales of costs orbicular- 
cordate to cordate, acute or acutish...........-. 4. O. guatemalensis. 
Veins 20 to 28 per centimeter; scales of costz smaller 
and darker, cordate-ovate or deltoid-ovate, acu- 
minate . 21... eee eee eee ec ee eee eet ee ee eeeee 5. O. lehmannii. 
Phyllopodia 1 to 3 (rarely 5) mm. long, usually thick, 
oblique and at first densely paleaceous like the rhi- 
zomes. 
Stipes wanting or nearly so, the lamina long-attenuate 
downward....... 2... e eee eee eee eee eee e tener 6. O. decurrens. 
Stipes 5 to 30 mm. long, the lamina sometimes narrowly 
cuneate, but always distinctly stipitate. 
Indusia ciliate. 
Veins 23 to 30 per centimeter; cilia of indusia 
long and persistent............---+---- 7. O. pilosa, 
Veins 16 or 17 per centimeter; cilia short and 
apparently few or caducous........-.-. 8. O. panamensis. 
Indusia not ciliate. 
Jostee barbate-squamose and long-hirsute...... 9. O. trujillensis. 
Costze neither barbate-squamose nor long- 
hirsute. 
Scales of costee mostly lanceolate and glan- 
dular-fimbriate........-...--- 10. O. trinitensis. 
Scales of costee deltoid, nearly all deeply 
lacerate-filamentose eeeeeeeceeeeees 11. O. costaricensis. 
1 Bot. Zeit. 9: 345-349. 1851. 
