SS 294 CHARACTERS OF TRIBES AND GENERA. 
allies, but are distinguished by the lower pair of venules of ` ` 
each fascicle anastomosing, forming a row of elongated ` ` 
transverse areoles on each side of the mid-rib, which 
character I originally considered to be only a simple state 
of Litobrochia ; I, however, now deem it best to adopt it 
as a transition genus between Pteris and Litobrochia. 
Sp. C. nemoralis ( Willd.) (v v.); C. biaurita, (Linn.) 
(v v.); C. geminata (Agardh.) 
Natives of the tropics of the Eastern and Western 
hemispheres, No less than thirty-eight synonyms are 
placed under C. biaurita by Dr. C. Luerssen. 
168.—Histiorreris, Agardh. (1839). 
Pteris sp. auct., Hook. Sp. Fil. 
Vernation  uniserial, distant ; sarmentum elongated, d 
generally epigeous and hirsute squamose. Fronds 1 to 8 
feet high, or sometimes scandent, and then ascending to 
15 or 18 feet, bi-tripinnate, smooth or glaucous beneath ; 
primary pinnæ and pinnules generally horizontally patent, 
always opposite and sessile, the lower pair of pinnules of 
each pinnæ often short and stipuliform, ultimate pinnules or 
segments entire, sinuose or pinnatifid. Veins anastomosed, 
or sometimes free. Receptacles transverse, continuous 
across the anastomoses of the venules, forming a linear, 
marginal sorus, furnished with an exterior attached, linear 
indusium, 
Type. Pteris vespertilionis, Labill. 
Ilust. Mett. Fil. Hort. Bot. Lips., p. 59, t. 14. 
OBs.—This genus consists of a few species of peculiar 
habit, differing from Litobrochia in the same manner that. 
Ornithopteris does from Pteris, in this case, as in others, 
habit being the most.obvious distinction, . 
