September 24, 19 14] 



NATURE 



lOI 



was published in 1810. I must pass over without 

 detailed remark the notable pioneer wonk of Allan 

 Cunningham, and of some others. The next out- 

 standing fact in the history of Australian botanv was 

 the voyage of Ross, with the Erebus and the Terror; 

 for wi.th him was Joseph Hooker, whose botanical 

 work gave an added distinction to an otherwise re- 

 markable expedition. 



The prime object of the voyage was a magnetic 

 survey, and this determined its course. But in the 

 intervals of sailing the Antarctic Seas the two ships 

 visited Ascension Island, St. Helena, the Cape, New- 

 Zealand, Australia, Tasmania, Kerguelen Island, 

 Tierra del Fuego, and the Falkland Islands. Thus 

 Hooker had the opportunity of collecting and ob- 

 serving upon all the great circumpolar areas of the 

 Southern Hemisphere. He welded together the results 

 results into his great work "The Antarctic Flora." 

 It was published in six large quarto volumes. In 

 them about 3000 species are described, while on 530 

 plates 1095 species are depicted, usually with detailed 

 analytical drawings. But these magnificent volumes 

 did not merely contain 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 systematically elaborated and com- 

 plete floras of the several countries. Moreover, in the 

 last of them, the "Flora Tasmaniae," there is an 

 introductory essay, in which the Australasian flora 

 was for the first time treated as a whole, and its 

 probable origin and its relation to other floras dis- 

 cussed. 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 com- 

 jpleted in November of that year, less than twelve 

 lonths after the joint communications of Darwin and 

 ^.Wallace had been made to the Linnean Society, and 

 )efore the "Origin of Species" was published. It 

 ras to this essay that Darwin referred when he wrote 

 that " Hooker has come round, and will publish his 

 belief soon." But this publication of his belief in the 

 mtability of species was not merely an echo of assent 

 [to Darwin's own opinion. It was a reasoned state- 

 i^ment advanced upon the basis of his own " self- 

 |thought," and his own wide systematic and 

 geographical experience From these sources he 

 Idrew support for "the hypothesis that species 

 fare derivative and mutable." He points out 

 piow the natural history of Australia seemed specially 

 suited to test such a theory, on account of the com- 

 jarative uniformity of the physical features being 

 iccompanied by a great varietv In its flora, and the 

 ?culiarity of both its fauna and flora, as compared 

 vith other countries. After the test had been made 

 |on the basis of the studv of some 8000 species of 

 slants, their characters, their spread, and their rela- 

 ions to those of other lands. Hooker concluded deci- 

 sively in favour of mutability, and a doctrine of pro- 

 ression. After readine this essay, Darwin wrote that 

 pt was to his judgment "by far the grandest and most 

 interesting essay on subjects of the nature discussed 

 have ever read." 



But beyond its historical interest in relation 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 everv island, 

 though thousands of miles of ocean may intervene. 

 Many of these species reappear in the mountains of 

 Southern Chili, Australia, Tasmania, and New Zea- 

 land. The southern temperate floras, on the other 



NO. 2343, VOL. 94] 



hand, of South America, South Africa, Australia, and 

 New Zealand 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 centre of creation of 

 new species in the Southern Ocean, in the form of 

 either a continent or archipelago, from which the 

 Antarctic flora radiated. From the zoological side a 

 similar difficulty arises, and the hypothesis of a land- 

 connection has been widely upheld^ and that it existed 

 as late as Mid-Tertiary times. The theory took a 

 rnore definite form in the hands of Osborn (1900), who 

 pictured relatively narrow strips of land connecting 

 respectively South America on one side and Tas- 

 mania and New Zealand on the other with the exist- 

 ing Antarctic land area. This would accord well 

 enough with the suggestion of Lothian Green, that 

 the plan of land-elevations on the earth is approxi- 

 mately tetrahedral; and it is, I believe, in line with 

 the views of those who are best informed on Antarctic 

 geography and geology, as studied from the land 

 itself. It may be hoped that further Antarctic dis- 

 covery may bring fresh facts to bear up>on this ques- 

 tion, for it is to the positive data acquired from studv 

 of the earth's crust that we must look, rather than 

 to the exigencies of botanists and zoologists, for its 

 final solution. 



But the hypothesis of an Antarctic land-connection 

 has been held open to doubt in various quarters. As 

 Sir Wm. Thistleton-Dyer has recentlv pointed out, 

 Darwin himself dissented, though regretfully, from 

 the sinking of imaginary continents in a quite reck- 

 less manner, and from the construction of land-bridges 

 in ever}- convenient direction. From the geological 

 side Dana laid down the positive proposition that the 

 continents and oceans had their general outline and 

 form defined in earliest time. Sir John Murrav, whose 

 recent death we so deeply deplore, was an undeniable 

 authority as to the ocean-floor. He wrote quite re- 

 cently with regard to Gondwana-land, that "the study 

 of ocean-depths and ocean-deposits does not seem in 

 any way to support the view that continental land 

 has disappeared beneath the floor of the ocean in the 

 manner indicated." He suggested that the present 

 distribution of organisms is better interpreted bv the 

 North Polar theory of origin. The "continuous cur- 

 rent of vegetation " southward at the present time 

 was recognised by Hooker himself, and definite 

 streams of northern forms have been traced by him 

 extending even to Australia and Tasmania. This 

 might account for much in present-day distribution ; 

 though it seems doubtful whether it would fully ex- 

 plain the extraordinar\- distribution of Antarctic 

 plants. The problem must for the present remain 

 open. 



This whole question, however, has a connection 

 with the still wider difficulty of the existence within 

 the Polar area of ancient floras. In the north the 

 fossils are even of subtropical character. Coal has 

 been found in lands with a five months' night. How 

 did such plants fare if the seasonal conditions were 

 at all like the present? To explain this it would be a 

 physiological necessity to assume either an entirely 

 different climatal condition in those regions from 

 that of the present time ; or. as has been suggested, 

 some shifting or creeping of the earth's crust itself. 

 These are, however, questions which we cannot under- 

 take to discuss with effect in the Botanical Section. 

 i We must not do more than recognise that an un- 

 solved difficulty exists. 



We pass now from Hooker's great work to the last 

 of the classical series, viz. the "Flora Australiensis " 

 of Bentham and Baron Ferdinand von Miiller. It is 



