CHARACTERS OF TRIBES AND GENERA. 135 
Oss.—This genus is founded on a solitary species, a 
native of Venezuela and Mexico, which in general habit 
agrees with Polybotrya, but is distinguished by the venules 
being combined, forming oblique elongated areoles. In 
general the sterile fronds are pinnate, with nearly entire 
pinne ; but in cultivated plants fronds are often produced 
with deeply laciniated pinnse, similar to the states observed 
in Olfersia. In these specimens the veins of each of the 
lacine are partially thickened, and more or less united ; 
and often towards the apex of the frond the lacine show 
some degree of contraction, and produce distant round 
masses of sporangia on their apex or margin, thus showing 
that the fertile fronds are only a highly contracted state of 
the sterile. ; 
Sp. S. serratifolium, Fée Acrost., t. 43 (v v.). 
51.—SrExosEMIA Presl (1836). 
Polybotrya sp. auct. ; Acrostichum sp. Hook. Sp. Fil. 
Vernation fasciculate, acaulose. Fronds few, erect, del- 
toid, ternately pinnate, 6 to 18 inches long, segments 
laciniately lobed, bulbiferous. Veins pinnate ; the lower 
venules transversely anastomosing, forming elongated costal 
and sub-costal areoles, the exterior venules free. Fertile 
segments linear, rachiform, involute, nearly wholly sporangi- 
ferous. 
Type. Polybotrya aurita, Blume. 
Illust. Hook; Gard. Ferns, t. 81; Moore Ind. Fil, p. 6B. ; 
J. Sm. Ferns, Brit. and For., fig. 41 ; Hook. Syn. Fil., 
t. 7, fig. 60, t. u. 
J . Ons.— This genus consists of a single species, a native of ` 
. the Malayan and Philippine Islands, which to a certain | 
extent in the character agrees with the following genus, © 
