388 BOTANICAL GAZETTE [MAY 
of geographical distribution, in which, as we have seen, he had at 
an early age become the leading authority. 
The fame of Sir JosepH HooKeER as a philosophical biologist 
rests upon a masterly series of essays and addresses. The chief 
of these were the introductory essay to the Flora Tasmaniae, 
dealing with the antarctic flora as a whole; the essay on the dis- 
tribution of arctic plants, published in 1862; the discourse on 
insular floras in 1866; The Presidential aii to the British 
Association at Norwich in 1868; his address at York, in 1881, on 
geographical distribution; and finally, the essay on the vegeta- 
tion of India, published in 1904. None of these were mere inspira- 
tions of the moment. They were the outcome of arduous journeys 
to observe and collect, and subsequently of careful analysis of the 
specimens and of the facts. The dates of publication bear this 
out. The essay on the antarctic flora appeared about twenty 
years after the completion. of the voyage. The essay on the 
vegetation of India was not published till more than half a century 
after Hooker first set foot in India. It is upon such foundations 
that HOOKER’s reputation as a great constructive thinker is securely 
based. 
The first-named of these essays will probably be estimated as 
the most notable of them all in the history of science. It was com- 
pleted in November 1859, barely a year after the joint communica- 
tions of DARWIN and WALLACE to the Linnaean Society, and before 
the Origin of species had appeared. It was to this essay that Dar- 
WIN referred when he wrote that ‘‘Hooker has come round, and 
will publish his belief soon.” But this publication. of his belief was 
not merely an echo of assent to DARWIN’s own opinions. It was a 
reasoned statement, advanced upon the basis of his “own self- 
thought,’ and his own wide systematic and geographical expe- 
rience. From these sources he drew for himself support for the 
‘hypothesis that species are derivative and mutable.” He points. 
out how the natural history of Australia seemed specially suited to 
test such a theory, on account of the comparative uniformity of 
the physical features being accompanied by a great variety in its 
flora, and the peculiarity of both its fauna and flora as compared 
with other countries. After the test had been made, on the basis 
_of the study of some 8,000 species, their characters, their spread, 
