25-1 CHAEACTEES OF TFJUES AND GENBEA. 



that their union under one tribe is far from being a natural 

 association of g-enera. I therefore now restrict the tribe 

 Biclsonice, as represented by the typical species D. arbores- 

 cens and its allies, and the genera Thijrsopteris, Cibotium, 

 and Balantium, the sjDecies of which amount in all to 

 fom'teen as at present known. 



136.— DiCKSONiA, L'Eerit. (1788). 

 Rooli. Sp. Fil., in part. 



Vernation fasciculate, erect, arborescent, criniferous. 

 Fronds bipinnate, 5 to 15 feet long ; pinnules pinuatifid, 

 Veins pinnate ; venules, free, simj^le. Beceptacles puncti- 

 form, terminal. Sori globose, large. Indusium bivalved, 

 coriaceous ; the outer valve (accessary indusium) concave, 

 cuoullate, conniving with the smaller, usually less cucullate, 

 inner valve, or special indusium, forming- an unequally 

 valved marginal cyst, including the sporangia. 



Type. DicJcsonia arhoresuens, L'Heril. 



lUust. Hook, and Bauer. Gen. Fil., t. 20 ; Moore Ind. 

 Fil., p. 77 A. ; J. Sm. Ferns Brit, and For., fig. 127. 



Oes. — This genus as here restricted consists of eight 

 known species of truly arboreus Ferns, some attaining the 

 height of 20 or more feet, the trunks of some becoming- 

 much enlarged by a coating formed of outgrowino- 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 Cyatltea, but as a genus they are technically 



* In the Addenda to ".Synopsis Filicuni " three new species are 

 described, two found in Xew Caledonia and one in Fiji and Saiiioa. 



