MAXON—STUDIES OF TROPICAL AMERICAN FERNS, 559 
Rhizome scales smaller, more rigid, mostly bicolorous, 
having a dark, often sharply defined, elongate or 
+» A-shaped median area of sclerotic cells. 
Rhizomes about 1 mm. in diameter, extensively 
creeping; rhizome scales about 0.5 mm. long, 
bearing from their center a conspicuous erect 
tuft of long, brown, bristle-like hairs. ....-...- 6. P. fallax. 
Rhizomes (except in no. 10) much stouter, up to 3 
mm. thick; rhizome scales much larger, lack- 
ing hairs. 
Lamina pinnately parted to pinnate, the seg- 
ments or pinne entire to pinnatifid. 
Lower surface of the lamina more or less com- 
pletely covered with imbricate scales, 
these partially concealing the sori. 
Lamina long-attenuate apically, sub- 
pinnatisect, the segments distant, 
mostly joined by a very narrow 
wing; scales of the lamina very 
numerous, densely imbricate, 
deeply fimbriate-lacerate, the 
teeth very deeply bifid.........- 7. P. xantholepis. 
Lamina obtuse or acute, pinnately 
parted, the segments closer, 
joined by a broad wing; scales of 
the lamina fewer, less imbricate, 
shallowly __lacerate-denticulate, 
the apices of the teeth entire or 
bipapillate. 
Segments 5 to 7 pairs, unequal; 
rhizome scales 2.5 to 3 mm. 
long, the cells of the slightly 
darker /\-shaped median line 
with delicate darkish sclerotic 
partition walls, a large lumen 
invariably present.........---- 8. P. subvestitum. 
Segments 1 to 3 pairs, subequal; 
rhizome scales more rigid, 1 to 
1.5 mm. long, the cells of the 
very dark and sharply defined 
/\-shaped median line very 
strongly § dark-sclerotic; lu- 
mina minute or obsolete. ....-. 9. P. fallacissimum. 
Lower surface of the lamina bearing few or 
numerous, mostly distant, often mi- 
nute scales, these not at all concealing 
the sori. 
Rhizome scales narrowly linear-del- 
toid, or long-acuminate or atten- 
uate from a deltoid-ovate base, not 
sharply fuscous-carinate and not 
at all repand or crispate. 
Scales of the lamina minute, almost 
linear, 4 to 7 cells broad....... 10. P. typicum. 
Scales of the lamina much larger, 
rounded-ovate to deltoid. 
