MAXON—STUDIES OF TROPICAL AMERICAN FERNS. 158 
reduced, the terminal segment conform or sometimes hastate and greatly enlarged; 
basal pinnze opposite, deltoid, very broadly and subequally cuneate or nearly trun- 
cate, 2 to 2.7 cm. long, about 2 cm. broad; middle pinne 3.5 to 4.5 cm. long, 1.5 to 
2.5 cm. broad above the broadly cuneate inequilateral base, asymmetrically deltoid or 
subtrapeziform, the apical portion triangular, acute; margins crenulate, distantly so 
toward the apex of the pinnw; venation subflabellate, the basal veins several times 
dichotomous, the others once or twice forked, very oblique, the branches nearly 
equal; sori 4 or 5 pairs, linear, 5 to 9 mm. long, very oblique, distinctly inframedial 
but usually extended along the anterior branch of the vein; indusium linear, about 
1mm. broad, fragile, entire, grayish brown; leaf tissue rigidly herbaceo-chartaceous, 
dull grayish green, discolored in drying, opaque, the venation distinctly visible only 
by transmitted light. 
Type in the U. 8. National Herbarium, no. 691213, collected on the Volcano Atitlan, 
Department of Solol4, Guatemala, February 16, 1906, ky Prof. W. A. Kellerman 
(no. 5792). 
Asplenium kellermanii departs very widely from the typical members of the group of 
A. trichomanes and perhaps ought not to be associated with them. It represents, in 
fact, one extreme of a series containing the large forms of A. monanthes as the other 
extreme, with A. melanorachis occupying an almost exactly intermediate position. 
From A. melanorachis it differs conspicuously in the characters enumerated in the 
key, and also in its paired sori, its subequal pinnz (the upper ones not or scarcely at 
all reduced), and in its large terminal segment.. Asplenium melanorachis itself is 
specifically distinct from A. monanthes, yet in its general habit, elongate-oblong 
pinne, and inferior sori it shows clearly an alliance with that species. It is said by 
Ghiesbreght to have grown upon the trunks of large trees. Aspleniwm kellermanii is 
terrestrial. 
THE NORTH AMERICAN TREE FERNS OF THE GENUS DICKSONIA. 
In the last paper of this series the writer published a key to the 
North American species of Cibotium, with notes upon the taxonomic 
history of the several species, which had been very generally con- 
fused. Related to Cibotium is the genus Dicksonia, whose species 
also have been widely misunderstood. The main differences between 
the two genera have recently been summarized in a nontechnical 
article! upon the tree ferns of North America. It is there pointed 
out that in Dicksonia the leaf blades are narrowly elongate and either 
lanceolate or oblanceolate, the lower pinne gradually reduced in 
size, while in Cibotium the blades are very much more ample and of 
a broadly ovate or deltoid type; a feature which is fully as important 
as the technical distinctions drawn from the indusia. The peculiar 
bivalvate indusium of the tribe Dicksonieae is also discussed briefly, 
reference being made to that of Cibotium as the most highly differ- 
entiated of any of the tribe, since in this genus the outer lip, like the 
inner, is manifestly cartilaginous. In Dicksonia, on the other hand, 
the outer concave lip consists merely of the leaf tissue of a small 
marginal lobule of the leaf segment, which is only slightly modified 
1Ann. Rep. Smiths. Inst. 1911: 463-491. pls. 1-15, 1912. 
