360 



SCIENCE 



[N. S., Vol. XL., No. 1028 



species are described, while on 530 plates 

 1,095 species are depicted, usually with 

 detailed analytical drawings. But these 

 magnificent volumes did not merely con- 

 tain reports of explorations, or descriptions 

 of the many new species collected. There 

 was much more than this in them. All the 

 known facts that could be gathered were 

 incorporated, so that they became system- 

 atically elaborated and complete floras of 

 the several countries. Moreover, in the 

 last of them, the "Flora Tasmanise," there 

 is an introductory essay, in which the 

 Australasian flora was for the flrst time 

 treated as a whole, and its probable origin 

 and its relation to other floras discussed. 

 Further, questions of the mutability and 

 origin of species were also raised in it. 

 The air was full of such questions in 1859 ; 

 the essay was completed in November of 

 that year, less than twelve months after 

 the joint communications of Darwin and 

 Wallace had been made to the Linnean 

 Society, and before the "Origin of 

 Species" was published. It was to this 

 essay that Darwin referred when he wrote 

 that "Hooker has come round, and will 

 publish his belief soon." But this pub- 

 lication of his belief in the mutability of 

 species was not merely an echo of assent to 

 Darwin's own opinion. It was a reasoned 

 statement, advanced upon the basis of his 

 ■"own self-thought," and his own wide 

 systematic and geographical experience. 

 From these sources he drew support for 

 "the hypothesis that species are derivative 

 and mutable." He points out how the 

 natural history of Australia seemed espe- 

 cially suited to test such a theory, on ac- 

 count of the comparative uniformity of 

 the physical features being accompanied by 

 a great variety in its flora, and the peculi- 

 arity of both its fauna and flora, as com- 

 pared with other countries. After the test 

 had been made on the basis of the study 



of some 8,000 species of plants, their char- 

 acters, their spread, and their relations to 

 those of other lands. Hooker concluded 

 decisively in favor of mutability, and a 

 doctrine of progression. After reading 

 this essay, Darwin wrote that it was to 

 his judgment "by far the grandest and 

 most interesting essay on subjects of the 

 nature discussed I have ever read." 



But beyond its historical interest in re- 

 lation to the "Origin of Species," Hooker's 

 essay contained what was up to its time 

 the most scientific treatment of a large area 

 from the point of view of the plant- 

 geographer. He found that the Antarctic, 

 like the Arctic flora, is very uniform round 

 the globe. The same species in many cases 

 occur on every island, though thousands 

 of miles of ocean may intervene. Many of 

 these species reappear in the mountains of 

 southern Chili, Australia, Tasmania, and 

 New Zealand. The southern temperate 

 floras, on the other hand, of South Amer- 

 ica, South Africa, Australia, and New Zea- 

 land differ more among themselves than do 

 the floras of Europe, northern Asia, and 

 North America. To explain these facts 

 Hooker suggested the probable former 

 existence, during a warmer period than the 

 present, of a center of creation of new 

 species in the Southern Ocean, in the form 

 of either a continent or an archipelago, 

 from which the Antarctic flora radiated. 

 From the zoological side a similar difSculty 

 arises, and the hypothesis of a land-connec- 

 tion has been widely upheld, and that it 

 existed as late as Mid-Tertiary times. The 

 theory took a more definite form in the 

 hands of Osborn (1900), who pictured 

 relatively narrow strips of land connecting 

 respectively South America on the one side 

 and Tasmania and New Zealand on the 

 other with the existing Antarctic land- 

 area. This would accord well enough with 

 the suggestion of Lothian Green, that the 



