512 
Willis. — Endemic Genera in Relation to Others. 
of Indo-Malaya, and only 19 in the 16 families that do not; they have 187 
in 39 families that occur on the African islands, and 37 in 30 families that 
do not. 
Postscript . Since writing the above, I have been working at the 
endemic genera of N. temperate America, and I find, as I shall show in 
a later paper, that the misunderstanding between Prof. Sinnott and myself 
is due to the fact that there are^ many relics there, while there are not in the 
tropics, to which most of the islands belong, nor in Europe. Each of us 
has reasoned from the territory that he has most closely examined. 
Literature. 
1. Arber (1919) : On the Law of Age and Area, in Relation to the Extinction of Species. Ann. 
Bot., xxxiii. 21 1. 
2. Sinnott (1916) : Comparative Rapidity of Evolution in various Plant Types. Amer. Naturalist, 
1. 466. 
3. (1917) : The Age and Area Hypothesis and the Problem of Endemism. Ann. Bot., 
xxxi. 209. 
4. (1917) : The Age and Area Hypothesis of Willis. Science, xlvi. 457. 
5. and Bailey (1914) : The Origin and Dispersal of Herbaceous Angiosperms. Ann. 
Bot., xxviii. 547 . 
6. (1915) : Foliar Evidence as to the Ancestry and Climatic Environment of 
the Angiosperms. Amer. Journ. Bot., ii. 1. 
7. Thwaites (1864) : Enumeratio Plantarum Zeylaniae. London. 
8 . Trimen (1893-1900) : Flora of Ceylon. 5 vols. London. 
9. Willis (1906) : The Flora of Ritigala. Ann. R. B. G. Perad., iii. 271. 
10. (1907) : Evidence against Natural Selection. Ibid. , iv. 1, 17. 
11. (1908) : Geographical Distribution of the Dilleniaceae. Ibid., 69. 
12. (1908) : The Floras of Hill-tops in Ceylon. Ibid., p. 131. 
13. (1911) : The Flora of Naminakuli-kanda. Ibid., v. 217. 
14. (1915) : The Endemic Flora of Ceylon. Phil. Trans. B., ccvi. 307, and correction in 
Proc. R. S., B., lxxxix, 1916. 
15. (1916) : The Evolution of Species in Ceylon. Ann. Bot., xxx. 1. 
16. (1916) : '1 he Distribution of Species in New Zealand. Ibid., 437. 
17. (1917) : The Relative Age of Endemic Species. Ibid., xxxi. 189. 
18. (1917) : The Distribution of the Plants of the Outlying Islands of New Zealand. Ibid., 
327% 
19. (1917) : Further Evidence for Age and Area. Ibid., 335. 
20. (1918) : The Sources and Distribution of the New Zealand Flora. Ibid., xxxii. 339. 
21. (1919) : The Flora of Stewart Island. Ibid., xxxiii. 23. 
22. (1919) : The Floras of the Outlying Islands of New Zealand and their Distribution. 
Ibid., 267. 
23. (1919) : On the Floras of certain Islets outlying from Stewart Island. Ibid., 479. 
24. (1920) : Plant Invasions of New Zealand, with reference to Lord Howe, Norfolk, and 
the Kermadec Islands. Ibid., xxxiv. 471. 
And cf. List of Literature in 20. 
