* 
398 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
cuneate (sometimes abruptly so); costa strongly elevated beneath, deciduously 
puberulous, noticeably but deciduously paleaceous at the sides, the scales reddish 
brown, deltoid, irregularly and deeply lacerate-filamentous; veins arising in 2’s or 
3’s, 18 to 24 per centimeter near the margin; sori rather large, situated 1 to 7 mm. 
from the costa, mostly arranged in an irregular row; indusia subpersistent, not ciliate, 
nearly or quite glabrous. Leaf tissue varying from membrano-herbaceous to rigidly 
herbaceous, lustrous, often iridescent, minutely glandular-pubescent beneath but 
soon glabrescent. 
Type in the U. 8. National Herbarium, no. 366014, collected in forest at La Palma, 
Costa Rica, altitude 1,459 meters, September 8, 1898, by A. Tonduz (no. 12551). 
ADDITIONAL SPECIMENS EXAMINED: 
Costa Rica: Orosi, Finca Valverde, alt. 1,400 meters, A. Brade 16836. La 
Fortuna, between Cervantes and Pacayas, alt. 1,400 meters, on tree trunks, 
March, 1906, Biolley. Helechales del General, Vallée du Diquis, alt. 700 
meters, Pittier 12011. Without locality, Cooper; Wercklé. 
The above description is drawn mainly from the type specimen and a second sheet. 
of the same collection, The additional specimens cited are mostly incomplete and 
either partially sterile or poorly dried, so that their reference here is attended with 
some doubt. They are like the type in minute characters, however, and especially in 
the characters afforded by the costal scales, which distinguish this species very clearly 
from the others here recognized. The older fronds appear to be glabrous; but it is 
possible in all cases to detect traces, at least, of the minute pubescence in protected 
places along the costa. The iridescent coloration, when present, is very striking. 
NOTES UPON POLYPODIUM DUALE AND ITS ALLIES. 
The Jamaican fern first described by Swartz in 1788 under the 
name Acrostichum serrulatum, and since known generally as Poly- 
podium serrulatum Mett., is one of a small group of species regarded 
by several writers in the past as constituting a separate genus, 
Xiphopteris, distinct from Polypodium. This group of species is not 
so recognized at present and can not be maintained as a valid genus, 
since there is nearly every gradation in form between its type species, 
“ Polypodium serrulatum,” and several small members of Polypodium 
(section Eupolypodium) related to P. trichomanoides. The name 
serrulatum not being available, however, for the type species just 
mentioned, the new name duale has been proposed by the writer in 
arecent paper. The full synonymy of P. duale is given below. 
The species which were associated with P. duale [P. serrulatum 
(Swartz) Mett.] by Hieronymus are treated in the following pages. 
Several of these, notably P. myosuroides, have been greatly mis- 
understood and neither Hieronymus? nor the writer * has heretofore 
been wholly successful in the effort to do away with existing con- 
fusion. In the present study the writer has had the advantage of 
examining most of the material in the Berlin herbarium, studied by 
Hieronymus, in addition to the ample series from Jamaica in the United 
States National Herbarium. But even with these specimens at hand 
‘Contr. U. 8. Nat. Herb. 16: 61. 1912. See also p. 399, below. 
* Hedwigia 44: 80-90. 1905. 
3 Bull. Torrey Club 32: 73-75. 1905. 
