APPENDIX 



499 



twelve species found in that continent. The other fact is the absence 

 of Uncinia from South Africa and from the African continent gener- 

 ally. One might have looked for a representative on Table Mountain 

 of a genus that has found a home on the isolated oceanic islands of 

 Tristan da Cunha and St. Paul, etc., on either side of the continent. 



Yet the absence of Uncinia from South Africa is quite consistent 

 with the usual behaviour of plants common to the southern part of 

 South America and the Australian and New Zealand region. Hemsley 

 gives a long list of plants (Chall. Bot., I., 52) illustrating the relation- 

 ship of these two regions. A large number of flowering plants 

 belonging to about ninety-three genera are included, the grasses 

 being excluded. The mode of presentation does not admit of one's 

 giving a precise numerical value to the results ; but it would appear 

 that not over one-tenth of the species common to the South American 

 and to the Australian and New Zealand regions occur in Africa. The 

 indications of the cyperaceous species in this list alone are very 

 suggestive. Out of a dozen species, belonging to six genera, all 

 either occur both in South America (mainly in the south) and in the 

 Australian and New Zealand region, or they are represented there 

 by closely related forms; but only two of them are also found in 

 South Africa. When dealing with Carex in Chapter XVI., it was 

 pointed out that of twenty-one Australasian species found outside 

 that region six occur in South America and only one in South Africa. 



It has already been remarked that the South American and New 

 Zealand centres of Uncinia are still in touch with each other, since 

 they hold a species in common and since species from the two centres 

 meet in the intervening islands. The point we are now concerned 

 with is the direction in which the inter-communication takes place ; 

 in other words, the direction in which species of Uncinia would be 

 likely to travel around high southern latitudes. The latitudes in- 

 volved correspond approximately with the zone of the Westerly 

 Winds, the belt of the Roaring Forties. Those who, like the writer, 

 have performed the voyage before the strong Westerlies from the 

 Cape to Australia in a sailing vessel and have watched the sea-birds 

 following in the ship's wake for weeks together will be in a position 

 to appreciate the influences at present determining the part taken 

 by the bird in distributing seeds in these latitudes. These sea-birds 

 travel around the globe in the belt of the Westerlies, and a case has 

 been recorded where a Cape Pigeon (Daption capensis), marked by a 

 ribbon around its neck, followed a ship for 5000 miles on its way 

 home from Australia by Cape Horn (Coppinger's Cruise of the Alert, 

 p. 18). Ever since 1888, when a letter of mine appeared in Nature 

 (May 10) concerning this matter, I have held the view that South 

 America has been a funnel from the Fuegian tip of which plants 

 have through the ages been detached and carried ever eastward 

 through the agencies of the westerly winds, the west-wind drift- 

 current, and sea-birds. The efficacy of the sea-bird in these lati- 

 tudes was brought home to me a few years before that date, when in 

 1881 I found a seed, apparently sound, in the stomach of a Cape 

 Pigeon caught by one of my mess-mates 550 miles east of Tristan da 

 Cunha (Nature, XXVI., 12; Chall. BoL, I., 45; IV., 313). 



