486 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
nukes all drawn out to long, slender, nearly lnear points, thus 
suggesting the species name; <A. microdonta, a lowland species 
already mentioned, easily distinguished by the remarkably large, 
strong, narrowly conical spines which occur at irregular intervals 
the whole length of its stipe and primary rachis; A. stipularis, a 
plant of the mountains of Costa Rica and western Panama, with a 
trunk 30 to 40 feet high and enormous spreading, nearly tripinnate 
fronds which show the very interesting adaptation of having the 
primary pinnes (particularly in the basal part of the blade) directed 
backward from their insertion upon the rachis at an acute angle; 
A. armata, which, with several related species, has the stipes and 
rachises densely soft-hairy; A. myosuroides, previously mentioned, 
with very minute, thickly set spines closely associated with an 
abundant covering of glossy brown, slender scales at the base of the 
stipe, and the pinnules of the deeply tripinnatifid fronds ending in 
narrow greatly elongate tips, ‘‘mouse-taillike,”’ as the specific name 
implies; A. Schiedeana, a much more leafy plant of Mexico and 
Guatemala, with broader and larger rounded segments; and A. 
Salvinii of Chiapas and Guatemala, a species with leaf blades fully 
tripinnate, the elongate, crenate, leathery segments sessile or short 
stalked, the rachises firm and woody and of a polished, dark 
purplish-brown color. The naked (nonindusiate) sorus of this 
group is indicated in plate 10, figure C, representing a portion of a 
very young pinnule of A. myosuroides, in which the sporangia are 
all in place. In figure D, of the same plate, is shown a similar por- 
tion of A. Schiedeana at a later stage, in which the sporangia are 
nearly all fallen away from the roundish elevated receptacle. 
The section Lophosoria contains a single species, Alsophila quad- 
ripinnata, which offers several peculiar structural characters, possibly 
warranting its separation as a distinct generic type; the trunk and 
fronds have already been described. 
The section Amphidesmium likewise contains a solitary species, 
Alsophila blechnoides, which is unique among American tree ferns in 
the production of more than one sorus upon the veinlets of its large 
simply pinnate fronds. A partial section of one of the long slender 
pinne of this species is shown in plate 13, figure A. Both this and 
the preceding species are peculiar in the silky hairlike scales of the 
rhizome and stipe, their form and structure being that of the tribe 
Dicksoniee and very different from the usual flat scales of the 
Cyathez. The fourth section, Trichipteris, which is essentially a 
group of fully bipinnate South American species, with sessile or 
stalked pinnules and sori borne in a dense row, is represented in 
North America by a single species, Alsophila marginalis, first described 
from British Guiana but gathered once since in Mexico. The scales 
in this section are like those of Eualsophila. 
