MAXON—STUDIES OF TROPICAL AMERICAN FERNS, 53 
segments being covered beneath by a rusty, usually dense, entan- 
gled tomentum, which, however, with age frequently becomes bleached 
and matted, or nearly disappears. 
The peculiarity of the Jamaican form here figured consists mainly 
in its having its simple pinne very narrowly linear (3 to 5 mm. broad) 
and merely subentire to broadly crenate, instead of pectinate, as in 
the normal form. The veins, which are short, are once-forked, the 
branches either simple or one or both of them again forked. The 
sori are dorsal upon the veinlets, as in all species of Dicranopteris, 
instead of terminal, as in Gleichenia. A dull brownish rusty tomen- 
tum closely invests the under surface of the pinne throughout from 
the narrowly revolute margins to the rachis. The primary internodes 
which subtend the pinne are precisely like those of the normal fronds 
of the species (Mazon 937), which were collected at the same time 
and place, except that they have in several instances a crenate or 
crenately lobed wing on the lower side, as well as upon the upper. 
The presence or absence of reduced segments bordering the primary 
and secondary internodes of the lateral branches of D. bifida is, how- 
ever, an unusually variable feature. 
Of almost identical form, but of very different covering below, is the 
plant described by Liebmann as Mertensia gleichenioides, Mertensia 
being used by him as the equivalent of Dicranopteris, and the species 
name gleichenioides in allusion to the general resemblance which the 
plant offers to true Old World Gleichenia. The lightly but broadly 
crenate pinne are a little more slender than in the monstrous form 
from Jamaica, not exceeding 4 mm. in width, and the margins are 
for the most part strongly revolute. The rachises of the pinne are 
clothed below with delicately lacerate pale ferruginous scales, and 
the veinlets of the under surface are covered with minutely dissected 
subpersistent scales, their capillary divisions exceedingly delicate 
and in mass strongly suggesting a tomentum. The veins are mostly 
once-forked, each of the branches again once or twice forked, the 
veinlets thus subfasciculate, a group to each broad crenation. 
That Liebmann’s plants represent an abnormal state of some 
Mexican species, as the monstrous state here figured does of D. bifida, 
is entirely probable, but the writer is unable to identify it with any 
previously described. For a very careful sketch of the two specimens 
constituting Liebmann’s type, and for a pair of pinne of the type, 
forwarded from the Botanisk Museum, Copenhagen, to the U. S. 
National Museum, the writer is indebted to the courtesy of Mr. Carl 
Christensen. 
As to the significance of the peculiar form shown by these two 
collections of different species, speculation is perhaps idle; yet it 
seems not unlikely that they represent a reversion to a more general- 
ized ancestral type, rather than a chance variation. And the suppo- 
sition that they may, perhaps, be an atavistic expression is doubtless 
