CHARACTERS OF TRIBES AND GENERA, 315 
Oss.—This genus is founded on a remarkable Fern, a 
native of Brazil, New Granada, and other parts of Tropical 
America, climbing to the tops of lofty trees, similar to the 
genus Lygodium. In the character of its fructification it 
does not differ much from Blechnum, but has the veins 
combined at the margin, and, with the peculiar nature of 
the indusium, which continues long permanent, and even 
enlarges in size after it has become reflexed, is sufficient fo 
mark this as a genus distinct from Blechnum. 
Sp. S. volubile, J. Sm. (v v.) (Hook. Gard. Ferns, t. 15). 
Tribe 93.—ASPLENIEZE. (Plate 23). 
Sori oblong or linear, oblique to the mid-rib or axis of 
venation. Sporangia produced on one side (unilateral) or on 
both sides of the same venule (bilateral), each furnished 
with a plane or vaulted lateral operculiform linear indu- 
sium, opening interiorly or exteriorly. 
Ozs.—In the “ Species Filicum" 307 species are described 
as belonging to this Tribe, but which in the “ Synopsis” of 
that work are reduced to 282; but in the Appendix to the 
Second edition 50 additional are recorded. They are found 
in all regions of the earth favourable to Fern life, some 
growing on cliffs or rocks, exposed to the extremes of heat 
and cold, others in shady ravines or caves, others on the 
ground or on trees, presenting great variation in the size 
and form of their fronds, which are generally fasciculate 
or rarely uniserial, the axis of vernation being generally 
acaulose, a few becoming subarborescent. The numerous 
. intermediate forms render it most difficult to arrive at any 
. Satisfactory conclusion as to the number of distinct species. 
In Moore's “Index Filicum” Asplenium occupies 70 pages, 
