CHARACTERS OF TRIBES AND GENERA. 125 



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 denned, 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 

 a 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 Phegopteridecp, which will be specially noticed under 

 the respective genera. 



Section 1. ELAPHOGLOSSE^E. 



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, entire, 

 sessile, or stipitate, from 2 inches to 2 J feet long, smooth or 

 squamose. Stipes often pseudo-articulate. Veins simple or 

 forked, their apices free and clavate. Fertile fronds mode- 

 rately contracted, the under side wholly sporangiferous. 



Type. Acrostichum conforme, Swariz. 



