MAXON—STUDIES OF TROPICAL AMERICAN FERNS. 399 
there remain several collections which can not be placed definitely at 
the present time. There will be, however, a decided advantage in fix- 
ing upon and illustrating the typical form of P. myosuroides, which 
apparently is confined to Jamaica, and the Jamaican species figured 
erroneously as myosuroides by Schkuhr and renamed Polypodiwm 
delitescens by the writer several years ago. With more ample material 
in the future it will be possible to determine whether either occurs 
upon the continent. 
The following key is adapted from that of Hieronymus: 
KEY TO THE SPECIES. 
Rhizomes conspicuously elongate; scales of the rhizome delicate, 
with thin, fulvous partition walls. ................------ | 1. P. duale. 
Rhizomes ascending; scales of the rhizome with thick, dark brown 
partition walls. 
Fertile fronds not sharply differentiated into two difform 
sterile and fertile parts...........--.---.-.2.------- 3. P. delitescens. 
Fertile fronds sharply differentiated into a caudate fertile 
terminal portion and a difform inferior sterile portion. 
Margins devoid of dark bristle-like hairs.......... . 6. P. wittigianum. 
Margins bearing minute, scattered, dark brown, bristle- 
like hairs. 
Sterile segments mostly oblong....... -eee-------- 2. P. myosuroides. 
Sterile segments more numerous, mostly of a deltoid 
type, often broader than long. 
Leaf tissue thin, translucent; marginal hairs few 
and very minute................------- 5. P. saffordit. 
Leaf tissue thick, nearly opaque; marginal hairs 
evident, though small and fragile .....-. 4. P. strictissimum. 
1. Polypodium duale Maxon, Contr. U. 8. Nat. Herb. 16: 61. 1912. 
Acrostichum serrulatum Swartz, Prodr. Veg. Ind. Occ. 128. 1788. 
Grammitis serrulata Swartz, Journ. Bot. Schrad. 1800 ?:.18. 1801. 
Asplenium serrulatum Swartz, Fl. Ind. Occ. 3: 1607. 1806. 
Gymnopteris serrulata Bernh. Neu. Journ. Bot. Schrad. 2?: 48. 1806. 
Xiphopteris serrulata Kaulf. Enum. Fil. 85. 1824. 
Micropteris serrulata Desv. Mém. Soc. Linn. Paris 6: 217. 1827. 
Micropteris orientalis Desv. Mém. Soc. Linn. Paris 6: 217. 1827, not Polypodium 
orientale Gmel. 1791. 
Polypodium serrulatum Mett. Fil. Hort. Lips. 30. 1856, not Swartz, 1801. 
Xiphopteris extensa Fée, Mém. Foug. 11: 14. 1866, not Polypodium extensum Forst. 
1786, Presl, 1825, nor Fée, 1869. 
Xiphopteris orientalis Fourn. Compt. Rend. 81: 1140. 1875. 
TYPE LOCALITY: Jamaica. 
DisTRIBUTION: Common nearly throughout the American tropics; occurs also in 
Africa (Kamerun, Sierra Leone, Mauritius, and Madagascar). 
ItLustraTions: Schkuhr, Krypt. Gewiichs. pl. 7, in part (as Grammitis serrulata); 
Hook. Exot. Fl. pl. 78 (as G. serrulata); Presl, Tent. Pter. pl. 9. /. 2. (as G. serrulata); 
Fée, Gen. Fil. pl. 10. B (as Xiphopteris serrulata); Fée, Mém. Foug. 11: pl. 19. f. 3 
(as Xiphopteris extensa). 
The present species, peculiar as it is in several particulars, appears to have been 
little understood by the early writers on ferns and not until 1856 was it placed in 
2797°—13-——2 
