436 GENERA OF FERNS. 
I retain as true Dicksonie, the outer or accessory indusium is 
much larger and concave than the special or interior indu- 
sium, and the two parts (or valves as they are sometimes 
called,) are but slightly connate at their base, therefore they 
form two distinct unequal valves, which is the only obvious 
distinction between Dicksonia, as here characterized, and 
those species with the nearly circular cup, and which have a 
creeping rhizoma as characterized under Sitolobium. L?Héri- 
tier’s other species (D. Culcita,) agrees in the structure and 
texture of the indusia, but differs in not being arborescent. 
I have therefore retained it as a type of the genus Balan- 
lium of Kaulfuss, and which may be considered to form the 
transition between Sifolobiun and Dicksonia, and also in its 
being the nearest in affinity with the solitary species which ` 
constitutes the following singular genus Thyrsopteris. 
117. Tuyrsopreris. Kunze. 
Veins pinnate; venules simple, direct, free and sporangi- 
ferous on their apices, forming soriferous pedicels. Indusium 
calyciform, entire, coriaceous, constituting globose, bacciform, 
free sori. Receptacle elevated, CHEER Sporangia sessile 
compressed. 
Rhizoma arborescent. Fronds decompound, multifid, the 
fertile portion contracted, forming a soriferous decompound 
thyrsus. 
Species. T. elegans, Kunze. 
Illust. Hook. Gen. Fil. t. 44. A. 
Obs. 'This rare and remarkable Fern was first discovered 
by the unfortunate Bertero in Juan Fernandez, and is said 
to have a caudex of the thickness of a walking-stick; but 
what marks it as peculiar, is the nearly total suppression of 
the cellular or foliaceous structure of the fertile portion of 
the frond, the veins being similar to peduncles, each fascicle 
constituting a small thyrsus of eight or ten globose sori, the 
indusium of each being formed by the union of the special 
and accessory indusia, which, as it matures, forms a com- 
plete circular cup; a structure closely resembling the 
