CHARACTERS OF TRIBES AND GENERA.  —«195 
. Species being arranged in natural groups, which are now 
. by most authors ranked as genera. They are distinguished 
from the preceding and following tribes by the sporangia 
not being produced in defined, round, or linear masses (sori), 
but closely occupying the whole of the under side of the . 
fertile fronds or segments, which are often contracted into 
rachiform spikes or panicles. By this contraction the 
venules are brought so close together that in many cases 
they seem to be entirely wanting, the whole disc becomes 
E sporangiferous receptacle; but in others this is a character 
of degree only, the contraction being often more or less 
definite in the same frond, there being instances of the 
veins being evident and sporangiferous, this variation has 
led to the different states being characterised by some ` 
authors as genera. Setting aside the contraction of the —— 
fertile frond, and the amorphous sori, many of the species 
. agree in natural habit and venation with genera of the 
tribe Phegopteridew, which will be specially noticed under 
the respective genera. 
Section 1.—ELAPHOGLOSSES. 
_ Fronds always simple. Veins free or rarely combined at 
the margin, or reticulate. 
40.—ELAPHOGLOSSUM. Schott. (1834). 
Acrostichum sp. Hook. Sp. Fil. 
= Vernation uniserial or fasciculate. Fronds simple, ibn 
i ends, or stipitate, from 2 inches to 23 feet long, smooth or 
| Squamose. Stipes often pseudo-articulate. Veins simple or 
i forked, their apices free and clavate. Fertile fronds mode- 
~ rately contracted, the under side wholly sporangiferous. 
~ Type: Acrostichum conforme, Swartz. 
