FLORA OP THE GALAPAGOS ISLANDS. 239 



(1), 622, to Chatham Islaud, is with scarcely a doubt an erroneous 

 determination. 



While it is thus clear that the Galapageiau flora is only an outlying 

 portion of the American flora with a strong specific differentiation, it is 

 impossible to trace its relationship closely to any one section of the 

 Pacific American vegetation. It can only be said in a general way that 

 nearly all the plants of the archipelago are identical with, or obviously 

 related to, species of the Sierras and Andes or of the Pacific Slope 

 between Lower California on the one hand and northern Chili on the 

 other. The xerophytic elements in the Galapageian flora show a con- 

 siderable resemblance to the desert flora of southern Peru and the drier 

 parts of the Andes. The mesophytes, on the other hand, correspond 

 most nearly to plants of Ecuador, Colombia, Central America, and 

 southern Mexico. 



These who have written upon the phytogeography of the Galapagos 

 Islands have frequently mentioned the West Indian affinities of the flora, 

 but here I can find no close resemblance or significant relationship. 

 It is to be noticed that Hooker, who first employed the term " West 

 Indian" regarding the flora of the Galapagos Islands, either used it to 

 include, or expressly qualified it by the addition of, the flora of Panama 

 and the adjacent lowlands of the continent, — a qualification which has 

 not always been sufficiently regarded by subsequent authors. But, on 

 the other hand, the discoveries of the last half century have shown, a 

 much greater difference between the flora of the Antilles and of the 

 Panama region than was to be inferred when Hooker wrote ; so although 

 a definite relationship can be traced between the Galapageian flora and 

 that of the lower slopes of Colombia, it does not follow that there is 

 any marked affinity to the flora of the West Indian Islands. Indeed, 

 of the species common to the Galapagos and the Antilles there are 

 none (if we except a sterile and doubtfully identified specimen of the 

 Cuban Cenchrus distichophyllus) which do not also occur upon the adja- 

 cent parts of the continent, and nearly all, like the halophytes of the 

 shores, are species of wide tropical-distribution. 



Hooker (4), 239, 250, drew attention to what appeared to be an inter- 

 esting double relationship between the plants of the Galapagos Islands 

 and those of other regions, as follows : " Here, as in other countries, the 

 vegetation is formed of two classes of plants, — the one peculiar to the 

 group, the other identical with what are found elsewhere. In this there 

 are even indications of the presence of two nearly equal Floras, — an in- 

 digenous and introduced, — and these are of a somewhat different stamp ; 



