l62 



NATURE 



[November i, 1917 



search of treasure. Associations such as these 

 were held sufficient to prove that it possessed 

 mag-ical power^ and this belief was reinforced 

 when after its destruction a visitation of plague 

 occurred, the bridge at Shuster collapsed, and 

 the Hawizah dam was breached. This was all 

 obviously the result of the desecration of the talis- 

 man, so the fragments were collected and buried 

 in the precincts of the tomb. The story, as a 

 whole, is singularly instructive to those in quest 

 of the origins of popular beliefs. 



OCEAN DRIFT FRUITS. 

 Plants, Seeds, and Currents in the West Indies 

 and Azores. The Results of Investigations 

 carried out in those Regions between 1906 and 

 1914. By H. B. Guppy. Pp. xi + 531. 

 (London : Williams and Norgate, 1917.) Price 

 255. net. 



THE author of this important work is a well- 

 known authority on ocean currents and the 

 geographical distribution of plants. His earlier 

 writings on the geology and natural history of the 

 Solomon Islands and the Cocos Keeling Islands, 

 and his more recent work on "Plant Dispersal," 

 contain the results of many years' patient and 

 exhaustive investigations in the Pacific region. In 

 the present volume he deals in an equally thorough 

 and careful manner with the numerous problems 

 connected with plant distribution in the Atlantic 

 region and embodies results of great scientific 

 interest. 



The dispersal of plants by ocean currents is by 

 no means a new subject of inquiry. Hemsley 

 ("Challenger Report: Botany," vol. i.) gives an 

 interesting summary of the literature to 1885. The 

 present author acknowledges that the reopening of 

 the subject by Hemsley was the means of stimulat- 

 ing the activities of himself and later investigators. 

 Clusius first figured some of the West Indian 

 drift seeds and fruits in 1605, though at the time 

 he was ignorant of their origin. Hans Sloane in 

 1695-97 g'ave an account of four drift seeds cast 

 ashore in the Orkney Isles. Three of these he 

 recognised as having been seen by him in Jamaica. 

 After the lapse of two centuries the mystery in 

 regard to the origin of the fourth drift fruit {Saco- 

 glottis amazonica) was only cleared up about 

 twenty years ago (see Nature, November 21, 

 1895). ^^^ numerous writers who have dealt with 

 drift fruits on European shores since Sloane are 

 fully enumerated in the third, possibly the most 

 ir^teresting, chapter in the book. The tracks of drift 

 seeds and fruits and the " fan-shaped " distribution 

 of bottle drift are admirably illustrated by a chart 

 of ocean currents (p. 46). The fact is established 

 that the drift brought by the north and main 

 equatorial currents and mingled in the Caribbean 

 Sea is captured by what ultimately becomes the 

 Gulf Stream and conveyed to the western shores 

 of Europe. Careful observation has shown that 

 at least one-third of the drift seeds and fruits 

 floating in the neighbourhood of the Turks Islands, 

 NO. 2505, VOL. 100] 



in the Caribbean Sea, have been found on the 

 coasts of Europe. Incidental mention is made of 

 the transport of logs of mahogany and even of 

 live turtles to European shores. 



In the fourth chapter the similarity between the 

 West Indian and West African littoral floras is 

 discussed. This may be accounted for by the 

 fact that of fifty-three plants occurring in both 

 worlds 62 per cent, respond to the current test 

 for transpK>rt by the main equatorial current. 



A detailed account of the large foreign drift 

 seeds and fruits, first of the Turks Islands and 

 secondly of other portions of the West Indies, 

 occupies several chapters. The distribution of 

 each is given and its relative capacity for disper- 

 sal by ocean currents. 



Interesting observations are made on Rhizo- 

 phora in the West Indies. In the appendix 

 (p. 502) it is suggested that vivipary of the man- 

 groves might be regarded as due to their 

 endeavour to accommodate themselves to climatic 

 conditions cooler than those that once prevailed 

 in their present habitat. 



The chapters on the general character and geo- 

 logical structure and the flora of the Turks 

 Islands embody the most complete account yet 

 published of the natural history of that interest- 

 ing group, and in the detailed study of the 

 altitudinal range of the indigenous plants of the 

 Azores we have two' scientific memoirs of great 

 interest. > 



It is not possible to devote adequate attention 

 to the chapter on Mr. Guppy 's theory of differen- 

 tiation based on the facts presented in this and 

 previous publications. In regard to the general 

 topic of the geographical distribution of plants, 

 he fully accepts the views of Bentham, Hooker, 

 and Asa Gray so clearly re-stated by Thiselton- 

 Dyer in his contribution to "Darwin and Modern 

 Science." Mr. Guppy admits that distribution 

 becomes purely a problem of the northern hemi- 

 sphere, and that this removes more difficulties in 

 the study of distribution than any other hypothesis. 

 It is a pleasure to add that the great value of 

 Mr. Guppy 's researches during the last thirty 

 years has been authoritatively recognised by the 

 recent award of the gold medal of the Linnean 

 Society. D. M. 



OBSERVATION, PHILOSOPHY, AND 

 TEACHING. 

 (i) The Comhination of Observations. By D. 

 Brunt. Pp. X + 219. (Cambridge: At the 

 University Press, 1917.) Price 8s. net. 



(2) Fundamental Conceptions of Modern Mathe- 

 matics. Variables and Quantities. With a 

 Discussion of the General Conception of Func- 

 tional Relation. By R. P. Richardson and 

 E. H. Landis. Pp. xxii + 216. (Chicago and 

 London : The Open Court Publishing Company, 

 1916.) Price 1.25 dollars or 55. net. 



(3) Revision Papers in Arithmetic. By W. G. 

 ' Borchardt. Pp. viii+ 156 + answers xxxii. 



(London : Rivingtons, 1917-) Price 25. 



