DERIVATION OF THE FLORA AND FAUNA 427 



be dug out from different depths, and if pollen of species not growing on the 

 island are found, some light will be thrown on the history of the flora. 



The map accompanying this paper was prepared by the Oceanographical 

 Institute in Goteborg. I am greatly indebted to the Director, Professor Hans 

 Pettersson, and to Dr. Borje Kullenberg for valuable assistance. 



May, 1956. 



Additions. 



P. 251. 



Usnea Gaudichaudii Motyka, known from the "espinal" of Central and North 

 Chile, is quoted for Juan Fernandez (Masatierra) by MOTYKA 34^. 600 as found 

 by Bertero, 1830. As its occurrence there seems little probable — Bertero 

 collected also near Valparaiso, etc. — I have excluded the species from my list. 



To Chapters IV and XVI. 



A recent paper by R. FURON, "Importance paleogeographique des mouve- 

 ments de subsidence du Pacific Central" (Rev. gen. des Sciences 62, 1955), should 

 be noted here. His object is expressed in the following terms: 



Constatant combien les biogeographes manquent de documentation geologique, il nous a 

 paru utile de regrouper les notions acquises au cours de ces dernieres annees, notions qui 

 eclairent fort bien I'historie du Pacifique depuis le Cretace (p. 307). 



Whereas the Galapagos Islands show, he says, a purely oceanic type of 

 rocks, andesitic basalt and tuff are found on Easter Island and andesite and 

 trachyte on Pitcairn. Contrary to what was told above, corals of Cretaceous age 

 were dredged in a depth of 2000 m on one of the Central Pacific guyots. The 

 deep borings through atolls, the latest on Eniwetok in 1953, have penetrated 

 through coral formations dating from Pleistocene to Eocene to the bedrock of 

 basalt, indicating a subsidence since the end of the Cretaceous of 2000 m. Perhaps 

 other parts of the Pacific would give still greater figures. 



To Chapter V. 



In the Proceedings of the Cotterwood Natur. Field Club 31, 1955, T. A. 

 Sprague gives an account of the Drift Theory of Du ToiT and finds that, from 

 a botanist's viewpoint, this theory "offers the best explanation hitherto brought 

 forward of the major problems of biogeography". With reference to the physical 

 side of the drift process he quotes Holmes' "Principles of Physical Geography" 

 (1944). In the case of Juan Fernandez, which certainly is one of the minor pro- 

 blems, I cannot see that the drift theory offers an acceptable solution. 



To Chapter VII, p. 360. 



An important paper by H. M0LIIOLM Hansen, "Life forms as age indica- 

 tors", Ringkjobing 1956, confirms the opinions of SiNNOTT & Bailev and others. 



