GENERA OF FERNS. 437 
genus Cyathea, with which it also coincides in the sporangia 
being compressed ; but its general character induces me to 
retain it in Dicksonie, with which it agrees through Balan- 
tium. The pedicellate calyciform indusium of Thyrsopteris, 
has much resemblance to that of Spheropteris, but in the 
latter genus the pedicel is a special organ, whereas, in Thyr- 
sopteris, it is merely an apparent pedicel, formed by the veins 
not being connected by cellular membrane, and therefore 
analogous to many species of Trichomanee. 
118. Crsotium, Kaulf. J. Sm. 
(Dicksonie sp. Sm. Pinonia, Gaud.) 
Veins forked or pinnate; venules direct, their apices free 
and sporangiferous. Jndusium of two coriaceous unequal 
valves, forming a reflexed adnate, bilabiate, cucullate cyst, 
constituting somewhat globose superficial sori. 
Rhizoma globose or arborescent. Fronds large, tripin- 
natifid, smooth, glaucous or pilose, lacinie equal. Sori su- 
berficially seated on the interior edge of the margin or sinus. 
Receptacle small. Sporangia pedicellate. 
Ezamp. 1. C. glaucum, Hook. et Arnott. 2. C. Chamissoi, 
Kawlf. (Pinonia splendens, Gaud.) 3. C. Schiedei, Schlecht. 
4. C. Barometz, J. Sm. (Aspidium Barometz, Hort. Ang. 
Balantium glaucophyllum, Hort. Berol). 
Ilust. Gaud. in Freyc. Voy. t. 21. Hook. et Bauer Gen. 
Fil. t. 25, 
Obs. This is a very distinctly marked genus, easily distin- 
guished from all other Dicksoniew by its remarkable horny 
gaping indusium, the outer valve of which differs in its man- 
her of attachment from the analogous valve or accessory in- 
dusium that characterizes the preceding genera, which, (as 
has been already stated,) is formed of the changed reflexed 
crenule, but in Cibotium it is produced on the outer base 
of the sporangiferous receptacle, exactly opposite to, and 
of the same structure as in the inner valve, and in that 
Case quite superficial and independent of the margin of the 
frond, except its mere attachment, In other respects 
