GENERA OF FERNS. 431 
pact by being formed of sessile sporangia produced on an 
elevated receptacle. "Therefore, considering that the direc- 
tion of the ring depends more upon circumstances connected 
with the attachment of the sporangia than upon real differ- 
ence of structure, I make no hesitation in retaining them in 
Polypodiacee. 
In Trichomanes spicatum of R. Hedwig, and T. elegans of 
Rudge, (in part) the fertile fronds are contracted, forming a 
simple distichous spike of sori; in the first, the cellular structure 
is so far obliterated or suppressed, that each venule becomes 
a free soriferous pedicel ; this form has been employed by Bory, 
for characterizing his genus Feea; but as transitions to the 
Same structure are observed in many other species of Tricho- 
manes, I therefore have not adopted Bory’s view. In T. ele- 
gans the fertile frond is in the form of a long, narrow, linear, 
membraneous rachis, bearing a row of tubular connate sori 
on each margin, which do not project beyond the connecting 
membrane ; this Fern Bory has also characterized as a genus, 
under the name of Hymenostachys, and which, setting other 
characters aside, might also not be considered worthy of 
notice as a generic character; but there is a very striking 
peculiarity to be observed in this species, that warrants its 
being retained as a distinct genus, which is in the venation 
being anastomosed, the only instance, to my knowledge, of 
anastomose veins in Trichomanee. 
110. Hymenostacuys, Bory. 
(Trichomanes sp. Auct. Didymoglossum, Desv.) 
Veins (of sterile fronds) forked; venules anastomosing ; 
Sort vertically oblong, terminal, produced within the margin 
of a contracted rachiform simple frond ; indusium urceolate ; 
sporangia sessile ; receptacle much elongated, filiform. 
Fronds from 6 inches to a foot in length, linear, the sterile 
frond pinnatifid, smooth ; segments linear-lanceolate, dentate; the 
ertile frond simple, stipitate, constituting a linear membra- 
nous soriferous rachis. 
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