TORREYA 



March, 1918 

 Vol. 18 No. 3 



THE c;p:nus (;lp:i(^henia (dicranopteris) in 



THE HAWAHAN ISLANDS 



By \'aughan MacCaughey 



The pteridophyte flora of the Hawaiian Archipelago com- 

 prises 43 genera and 185 or more known species; of these 2 genera 

 and 118 species are endemic. There are 18 genera with 75 per 

 cent, or over of endemic species; 18 genera either possess no 

 endemic species, or have 75 per cent, or over of non-endemic 

 species.* In this rich and extremely interesting fern flora the 

 genus Gleichenia {Dicranopteris) holds a unique position with 

 reference to range and ecology. Whereas the great majority of 

 the Hawaiian ferns are of small stature and of scattering occur- 

 rence, the Gleichenias form solid and extensive thickets and 

 jungles, almost impenetrable (owing to the peculiar growth- 

 habits of these plants), and occupying hundreds of acres. There 

 are four species in the Hawaiian flora, of which two are endemic, 

 and two are found in other countries. The ubiquitous and 

 dominant character of Gleichenia dichotoma, for example, has 

 made it a serious pest in the montane forests. The Gleichenias, 

 in terms of both bulk and area, are at the present time the most 

 abundant ferns in the Hawaiian forests, not even excepting the 

 tree-ferns, t which were formerly much more plentiful than at 

 present. 



It is the purpose of the present paper to give a succinct account 

 of this remarkable fern genus, with descriptions of the Hawaiian 



* For further data see MacCaughey, Ecological Survey of the Hawaiian Ptcrido- 

 phytes, Journal of Ecology; in course of publication. 



t MacCaughey, The Tree F"crns of Hawaii, American Botanist 22: 1-9, i(;i6, 

 2 figs. 

 [No. 2, Vol. i8 of ToRREYA, comprising pp. 21-40, was issued 8 March, 1918.] 



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