CHAPTER m 



DICKSONIA, Vmritier. 

 (Dick-so'-m-a.) 



HE genus Dicksonia, which forms by far the most hxiportant 

 division of the tribe Dicksoniew, was named in honour of 

 James Dickson, a famous British cryptogamic botanist. It 

 was first proposed by L'Heritier, in 1788, for two species— 

 D. culcita^ a native of the Azores and Madeira, and 

 D. arhorescens of St. Helena. In these two species the involucre (covering 

 of the spore masses) is distinctly two-valved, the outer valve being formed 

 from the apex of a lobe or segment. In 1801 Bernhardi proposed a genus 

 Dennstmltia ; but this was promptly rejected by Schkuhr and Willdenow, 

 and the plants belonging to it were referred to Dicksonia, which, by 1810, 

 was made to embrace as many as twenty species. The authors of the 

 " Synopsis FiHcum," in which work it is given as Genus 13, further enlarged 

 Dicksonia by adding to it the species of Cibotium, but these have the outer 

 half of the involucre separate from the lobule. 



The genus Dicksonia, as it stands at present, includes the following 

 sections : 



Balantium (Bal-an'-ti-um), Kaulfuss and J. Smith, the characters of which 

 are similar to those of Eudicksonia. 



Cibotium (Cib-o'-ti-um), Kaulfuss, in which the involucre is distinctly 

 two-valved, the outer valve being coriaceous (leathery) and distinct from the 

 substance of the frond. 



