242 PROCEEDINGS OF THE AMERICAN ACADEMY. 



flora of the archipelago. Altogether there have been 72 families ^ of 

 flowering plants and ferns found on the islands. Of these families 39 

 include endemic forms, and 33 contain only plants common to other 

 regions. Excluding some indeterminate forms, there are 232 genera 

 of pteridophytes and spermatophytes upon the islands. 



Notwithstanding the uncertainty with which some plants are here 

 reckoned as species, and others as varieties or forms, the following figures 

 regarding the plants of the Galapagos Islands will have an interest : 



Of endemic ferns there are only 3, that is, but 5 per cent. Of endemic 

 spermatophytes there are 202 species, 15 varieties, and 19 forms, — a 

 total of 236, that is, 44.4 per cent of the whole flowering flora. The 

 total number of vascular plants which are endemic is 239, or 40.5 per 

 cent. Of these endemic plants 130, that is, more than half, are con- 

 fined to a single island. 



The ratio of (determined) species to genera is as 2.16 : 1. 



The ratio of species, varieties, and forms to genera is as 2.55 : 1. 



It is noteworthy that, although there is such a high percentage of 

 peculiar forms, varieties, and species, there is no corresponding peculiarity 

 among the genera of these islands.^ Of the several genera which have 

 from time to time been characterized as exclusively Galapageian, only 

 two, Scalesia and Lecocarptts, are now maintained, while all the others 

 have been reduced to genera of continental America, with the single ex- 

 ception of Macraea, which falls into a genus of the Hawaifan Islands. 

 Even Scalesia is not a strong genus, as it is not easy to show very sharp 

 generic distinctions between it and some allied Helianthoideae in Mexico 

 and Central America. 



1 This does not include the Rosaceae and Bignoniaceae, which rest, so far as their 

 Galapageian occurrence is concerned, upon single and doubtful determinations. 



2 Tlie statement of Darwin (2), 1G5, regarding the genera of Compositae, is, as 

 pointed out by Mr. Henisley, quite erroneous, and must have rested upon some 

 misapprehension of data furnished him. 



