MAXON—STUDIES OF TROPICAL AMERICAN FERNS. 575 
ticulars, notably in its strongly cartilaginous leaf margins and in the character 
of its scales. The rather wide-creeping rhizome (2 to 8 mm. in diameter) has 
a very dense covering of closely imbricate scales. These are mostly roundish- 
ovate to broadly oblong, 1.5 to 2.5 mm, long, acuminate, fragile, conspicuously 
and narrowly fuscous-carinate, the broad, pale brown borders distinctly repand 
but scarcely complicate-crispate, the margins irregularly erose. The scales of 
the lamina are numerous, but mostly not contiguous, 1 to 1.5 mm, long, deltoid- 
ovate, abruptly long-attenuate, pale brown, with a darker center, coarsely and 
deeply denate, the teeth bipapillate. They agree fairly well with the rough 
drawing of the scales of P. tweedianum given by Hooker, much better, in fact, 
than do those of specimens referred to P. tweedianum by Hieronymus, 
Hieronymus* has mistakenly listed under P. tweedianum at least two 
specimens (Rusby 352, 3538) which the writer believes to represent a new 
species, P. rusbyi (p. 570). The plants so referred have the fronds larger and 
decidedly more lax than those shown in Hooker’s plate, with the segments less 
ascending, even spreading, They clearly do not pertain to Hooker’s species. 
Christ reported P. tweedianum from Costa Rica in 1906? upon the basis of 
specimens collected by Wercklé, Pittier (840, 13257), and Tonduz (16716), 
although at least one of these numbers (Pittier 18257) had previously * been 
listed by him as belonging to his new variety, Polypodium plebejum costari- 
cense. Subsequently * this variety was reduced by him to P. leucosticton, in 
which species, aS now understood, it is certainly to be included. Under these 
circumstances it is exceedingly doubtful if P. tweedianum should be recog- 
nized as a member of the North American flora. No specimens from this 
region have been seen by the writer, at least. 
EXPLANATION OF PLate 39.—Bolivian specimens of Polypodium tweedianum (Fiebrig 
3625, U. S. Nat. Herb. no. 694023; ex Herb. Gray). Scale 3. 
19. Polypodium guttatum Maxon, sp. nov. Prate 40. 
Rhizome wide-creeping, mostly hypogean, tortuous, rarely branched, 2 to 3 
mm. in diameter, freely radicose on all sides, densely paleaceous, the scales 
fragile, closely impacted, broadly ovate-oblong, 1 to 1.5 mm. long, yellowish, 
deeply fimbriate-lacerate, crispate, with a linear or very narrowly triangular 
median stripe of elongate blackish cells, these having the outer walls semitrans- 
lucent and the partition walls blackish and very strongly sclerotic, the lumen 
often obsolete. Fronds few, 1 to 3 em. apart or two borne together, 15 to 35 
cm. long, erect; stipe 10 to 20 cm. long, 1 to 1.5 mm. thick, yellowish to pale 
olivaceous or darker at the base, subterete to angulate, faintly foliaceo- 
marginate, or noticeably so at the apex; lamina narrowly to broadly oblong 
or deltoid-oblong, acute, rather abruptly short-caudate, 7 to 22 cm. long, 4 to 12 
em, broad, subpinnatisect throughout, the stout stramineous rachis very strongly 
elevated ; segments 12 to 16 pairs, patent, linear to linear-oblong, often narrowed 
just above the base, obtuse or acutish, 4 to 10 mm. broad, the lower ones once 
or twice their width apart, those above gradually closer but never contiguous, 
all of them dilatate or at least decurrent, connected by an oblique foliaceous 
wing 0.5 to 2 mm. broad upon each side of the rachis; margins strongly callous, 
minutely and remotely notched, repand in drying; veins 14 to 18 pairs, con- 
cealed, free, spreading, 2 to 4-forked, the large sori terminal upon the elongate 
first branch, slightly nearer to the margin than to the midrib. Leaf tissue very 
1Bot. Jahrb. Engler 34: 520, 521. 1905. 
* Bull. Herb. Boiss. II. 6: 50. 1906. 
. * Bull. Herb. Boiss. II. 5: 4. 1905. 
*Bull. Soc. Bot. Genéve II. 1: 219. 1909. 
