380 GENERA OF FERNS. 
Obs. This rare fern was discovered by Mr. R. Brown in 
the year 1802, on the shores of the Gulf of Carpentaria and 
east coast of New Holland, where we believe no collector has 
met with it since; but it appears, on the authority of speci- 
mens in the herbarium of Sir W. J. Hooker, to be also a 
native of Madagascar. I have already noticed that its 
possessing simple fronds is the only character to distinguish 
it, as a genus, from the following. 
127. GLEICHENIA, Sw. Willd. Presi. 
(Calymella, Presi.) 
Veins pinnate, or pinnately forked. Venules free, the lower 
exterior one fertile. Sporangia terminal, 2 to 4, superficial 
or immersed in a concave cyst, forming round sori. Pinnules 
either plane or revolute and cucullate, constituting an uni- 
versal indusium. 
Fronds from 6 inches to 11 foot high, usually rigid, once or 
oftener dichotomously branched, the branches (or pinne) pin- 
natifid or pinnate ; pinnules or lacinie minute, plane or plicate 
and concave, smooth, glaucous, tomentose or squamose. Sori 
Examp. 1. G. polypodioides, Sw. 2. G. rupestris, R. Br. 
3. G. alpina, R. Br. 4. G. microphylla, R. Br. 5. G. dicarpa, 
R. Br. 6. G. heciostophylla, A. Cunn. 
Tust. Hook. gen. fil. t. 41. A.B. Hook et Grev. ic. fil. t. 58. 
Obs. From the above character, it will be observed that 
the sporangia are either superficial or immersed; which dif- 
ference Presl has adopted for constituting two genera; re- 
taining M Gleichenia those individuals with immersed 
. Son, and placing, under his genus Calymella, two species 
characterised as possessing superficial sori. But a careful exa- 
iamtion of the species induces me to think that this pecu- 
harity is not worthy of consideration as a generic distinction, 
more especially since all the species agree in habit. 
The immersed sori are well exemplified in Gleichenia poly- 
podioides ; in that species the sori consist of four decussate 
sporangia sunk in a round cavity, each sporangium being 
