48 T O R R E Y A 



A\'e now come to a region which has played a prominent part in taxonomy, 

 the Galapagos Islands and the adjacent coast of South America. These islands 

 were visited by Darwin in 1835, and upon the variations of birds and tortoises 

 from island to island, as well as upon the plants which were named by the 

 vounger Hooker, were laid the foundations of evolution by geographic isola- 

 tion. The plants were briefly discussed by Darwin in the "Origin of Species'' 

 (p. 349) : "Dr. Hooker has shown that in the Galapagos Islands the propor- 

 tional numbers of the dififerent orders are very different from what they are 

 elsewhere. All such differences in number, and the absence of certain whole 

 groups of animals and plants, are generally accounted for by supposed differ- 

 ences in the physical conditions of the islands ; but this explanation is not a 

 little doubtful. Facility of immigration seems to have been fully as important 

 as the nature of the conditions. 



"Manv remarkable little facts could be given with respect to the inhabitants 

 of oceanic islands. For instance, in certain islands not tenanted by a single 

 mammal, some of the endemic plants have beautifully hooked seeds ; yet few 

 relations are most manifest than that hooks serve for the transportal of seeds 

 in the wool or fur of quadrupeds. But a hooked seed might be carried to an 

 island b}' other means ; and the plant then becoming modified would form an 

 endemic species, still retaining its hooks, which would form a useless appendage 

 . . . trees growing on a continent, might, when established on an island, gain 

 an advantage over other herbaceous plants by growing taller and taller and 

 overtopping them. In this case, natural selection would tend to add to the 

 stature of the plant, to whatever order it belonged, and thus convert it into a 

 bush and then into a tree." 



It is interesting to note in this connection that the only genus of plants now 

 recognized as endemic to the Galapagos Islands is Scalesia. which is bushy or 

 sometimes nearly herbaceous in the lower parts of the islands, but some species 

 become large trees where the moisture is more plentiful. Stewart in 1911 esti- 

 mated that 40 percent of the plants (varieties and forms being included in 

 the count), were endemic, but as in the case of the birds, the larger percent 

 of the endemic plants occur in a few groups. Many supposed endemics, further- 

 more, have been recently found on the desert coasts of Ecuador and northern 

 Peru ; these areas have a climate strikingly similar to that of the Galapagos 

 Islands, and together with the islands seem to form a marked geographic 

 province. Taxonomic problems which vex the botanist have cropped up among 

 the ornithologists. For example. J. Huxley writes of Swarth (quoted by Gold- 

 schmidt in "'The ^Material Basis of Evolution,'" p. 209), "after classifying them 

 [the Galapagos finches] into five different genera with over thirty species and 

 subspecies. ... it would be almost as logical to put them all in one genus and 

 species." So far as the Galapagos are concerned the astoimding extremes of 



