/ CHARACTERS OF TRIBES AND GENERA. 
that their union under one tribe is far from being a natural E 
association of genera. I therefore now restrict the tribe 
— Dicksonie, as represented by the typical species D. arbores- 
cens and its allies, and the genera Thyrsopteris, Cibotium, 
and Balantium, the species of which amount in all to 
fourteen as at present known. 
136.—D1cxsoxu, L’ Herit. (1788). 
Hook. Sp. Fil., in part. 
Vernation fasciculate, erect, arborescent, criniferous. 
Fronds bipinnate, 5 to 15 feet long; pinnules pinnatifid. 
Veins pinnate; venules, free, simple. Receptacles puncti- 
form, terminal. Sori globose, large. Indusium bivalved, 
coriaceous ; the outer valve (accessary indusium) concave, 
cucullate, conniving with the smaller, usually less cucullate, 
inner valve, or special indusium, forming an unequally 
valved marginal cyst, including the sporangia. 
Type. Dicksonia arborescens, L'Herit. Ae 
Tilust. Hook. and Bauer. Gen. Fil., t. 20; Moore Ind. LB 
Fil., p. 77 A. ; J. Sm. Ferns Brit. and For., fig. 127. 
Oss.—This genus as here restricted consists of eight ` ` 
known species of truly arboreus Ferns, some attaining. the ` E. 
beight of 20 or more feet, the trunks of some becoming 
much enlarged by a coating formed of outgrowing aerial 
rootlets. ‘They have a wide geographical range, the typical 
species being found only in St. Helena, one in Java, one in 
Tropical America, one in Juan Fernandez, Fiji, and New ` ` 
` Caledonia, two in New South Wales and Tasmania, and ` 
_ three in New Zealand.* In habit and general appearance ` 
. they resemble Cyathea, but as a genus they are technically ` 
- In the Addenda to ''Synopsis Filicum " three new species are ; 
described, two found in New Caledonia and one in F iji and Samoa. — 
