338 



C. SKOTTSBERG 



quarie plants have, TAYLOR states, propagules suited to bird transport. It is sur- 

 prising that Werth {317), who made a detailed study of the Kerguelen flora, 

 asserts that not one of the flowering plants possesses any special dispersal mech- 

 anism for either wind, water or bird carriage. Still, the two islands have some 9 

 species in common [^^4). Taylor's conclusion that, "if longdistance dispersal 

 has occurred on Macquarie Island, then it could well have occurred elsewhere" 

 is certainly correct; we know, for one thing, many wide-spread sea-side plants 

 and a number of widely dispersed aquatic species, possibly transported by 

 migratory birds. South Georgia is in much the same situation as Macquarie, 

 but still rather heavily glaciated thanks to its great altitude, and the possibility 

 that any higher plants survived the Glacial epoch is very small indeed, whereas 

 indications that many mosses and lichens date from preglacial times are strong. 

 The vascular flora is poorer than on Macquarie, and there are no endemic species. 

 When Taylor accuses me of having argued against all overseas migration also 

 n this case he must have misunderstood me. I expressly took this possibility 

 into account in the paper he quotes {226). 



Wallace calls attention to sea birds breeding on islands in the tropics; 

 Phaeton makes its nests on the Hawaiian Islands in 4000 ft. altitude and also in 

 the highland of Tahiti, and such birds would account for the similarity of the 

 mountain floras. In reality these floras have practically nothing in common. 

 Miss GlBBS {321), discussing the origin of the montane flora of Fiji, refused to 

 regard birds as capable agents; wind may have been more efficient. 



No modern zoologist has tried to defend the theory of unlimited overseas 

 migration with greater zeal than Zimmerman. In his Introduction to "Insects of 

 Hawaii" we read: 



There is no evidence whatsoever to support the contention that they (i.e. the Ha- 

 waiian Is.) are of continental origin or character, or that they were ever joined together 

 in an elongate subcontinental land-mass or even in a continuous subaerial mountain 

 range [2gS. 6). 



And, in opposition to certain other biologists he refuses to regard the islands as 

 old, they are at most Pliocene and no part of them older than five million years; 

 most of the lava is younger, the bulk of the land Pleistocene. He is opposed to 

 my ideas but he thinks that the explanation ofl"ered by him will, partially at least, 

 reconcile the differences between us. In an earlier paper (Amer. Naturalist jG, 

 1942), to which he refers, he spoke of former high islands, other than those found 

 on maps, which once existed; once more the "stepping-stones routes" are called 

 to life. Atolls are the remnant of many of them, or reefs like among the Leeward 

 islands of Hawaii, and such preexisting islands would account for the immigration 

 from all directions. He does not call for jumping of thousands of miles of open 

 sea, but rather for series of shorter over-water steps. I am afraid that we need 

 some substantial refurnishing of the Pacific basin to supply a sufficient number 

 of intermediate stations. Not all of these routes were, he says, available at the 

 same time, and this would explain the apparent difference in age of various 

 sections of the biota (pp. 51, 52). Most of the roads were cut off" in Pliocene and 



