33° 



C. SKOTTSBERG 



of the size and enormous climatic amplitude of these families — the preponder- 

 ance, in nearly all floras of dicotyledons (2 V2 to 4 times as many as the mono- 

 cots), and the absence of any strongly marked South Pacific flora south of Hawaii 

 and east of New Guinea, New Caledonia and New Zealand (which ought to show, 

 I suppose, that the island swarms are not fragments of a larger land mass). Good 

 continues p. 74: 



A common expression of the theory of continental drift postulates that the sunder- 

 ing of various continental masses began in a relatively remote geological period and 

 that it has continued without notable cessation ever since. The distribution of Angio- 

 sperms does not seem to be in special accordance with any such particular course of 

 events. It suggests more strongly that sundering occurred after these plants as a group 

 had become well diffused, let us say by the Eocene. Similarly I know of nothing in 

 the distribution of Angiosperms to show that drift is still going on. Can it be that 

 continental drift has in fact been, not a persistent process, but an intermittent feature 

 of geological time, as for instance have the great glaciations? If so, and if it can 

 further be shown that the most recent of these drift ages took place not earlier than 

 the beginning of the Tertiary, then at last the plantgeographers will have to hand a 

 master-key to most of his perplexities. 



It will be difficult to shape a key that will fit a lock constructed in this fashion. 

 As the glacial periods were interrupted by interglacial periods, so the periods 

 of sundering should have been interrupted by periods not of a standstill but of 

 the land-masses coming into contact again, last time during the Jurassic-Creta- 

 ceous era, which saw the origin, evolution and dispersal over the globe of the 

 Angiosperms, to be followed by the last drift age. 



With regard to tlie relations and disjunctions between South America (with 

 Juan Fernandez, etc.) and Antarctica, Australia and New Zealand, vertical move- 

 ments seem to offer a less distant possibility. 



In a most cleverly written chapter GoOD [log. 344-360) discussed land- 

 bridge versus continental drift. If we cannot, he says, accept the former, nor 

 put our trust in dispersal, a changing position of the continents is the only way 

 out of the difficulties. This may be true, but we have seen that this theory does 

 not help us to solve the problem concerning the oceanic islands. Gordon [iiJ] 

 points out that the occurrence of a small but important subantarctic element in 

 the Pacific, reaching north to the Hawaiian Islands where it is better displayed 

 than in any of the Polynesian or Melanesian groups, makes it impossible to deny 

 both land-bridges and the efficiency of transoceanic dispersal without providing 

 for migration with the hel[) of shifting continents. GooD 



has run into an impasse over the Pacific islands like Hawaii. He has rejected the land- 

 bridge hypothesis in favour of continental drift. . . . But he excludes continental drift so 

 far as the islands are concerned, for he accepts them as truly oceanic, not continental frag- 

 ments. Yet he will not accept overseas migration. Well, I can't see what explanation 

 remains, if all these three are excluded, but the plants are there (p. 148). 



WULFF {2gi) found that the biogeographers have good reason to support 

 Wegener's theory; much speaks against it, but he trusts that the difficulties 

 will be overcome by and by. He recognized that, with regard to the Pacific, 

 they are very considerable and call for a modification of the theory. 



