280 THE VOYAGE OF H.M.S. CHALLENGER 



Naturalised in Africa and Asia. 



Hibiscus tiliaceus, Linn. 

 Acacia famesiana, Willd. 



Guilandina bonduc, Linn. 

 A lirus precatorius, Linn. 

 Saxvola lobelia, Linn. 



Rhizophora mangle, Linn. 1 

 Batatas pentaphijlla, Choisy. 



Origin Asiatic or African. 

 Naturalised in America. 



Batatas paniculata, Choisy. 

 Ipomosa pes-caprce, Sweet. 



Transported from the Old World into the New, or the reverse ; but of doubtful origin. 



Telaiithera frutescens, Linn. 

 Stenotaphruiii americanum, Schranck. 



Sporobohis virginicus, Kunth. 



Common to Asia, Africa, and America, without any clue to its origin. 

 Canavalia obtusifolia, DC. 



The majority of the plants in the preceding list come under consideration in this work, 

 and many of them are now known to have a much wider range than De Candolle attri- 

 buted to them, particulars of which may be found by consulting the indexes to the various 

 parts. Others, such as Remirea maritima and Abrus precatorius, although not coming 

 within the scope of this work, are very widely dispersed in maritime districts. 



The lack, however, of reliable and circumstantial evidence of the dispersion of plants 

 by oceanic currents was commented upon by De Candolle in the admirable work named, 

 and since the date of its publication (1855) the subject has received considerable attention, 

 though, as the secpiel shows, very much remains to be done before we shall be in a position 

 to measure the probable extent of oceanic influence in the dispersion of land plants. Too 

 many writers have generalised on the topic, without recording the data upon which then- 

 generalisations were founded. This was not due, doubtless, to a want of observation, but 

 rather to inappreciation of the importance of recording, at the time of observation, 

 facts trifling in themselves taken separately, but significant in the aggregate. Darwin 

 very fully realised on his travels the necessity for actually noting small facts, and he 

 thereby provided himself with materials for a lifelong study ; and his example has been 

 followed by many of the most successful of living naturalists. At p. 113 of the Report 

 on the Botany of the South-eastern Moluccas, will be found a list of the plants collected 

 by Darwin in the Keeling Islands, all of which he regarded as having been transported 

 thither by the waves of the sea ; and further evidence of the action of the sea in various 

 parts of the world substantially confirms this view. The question arising again after his 

 return home, he carried out and published 2 the results of a series of experiments to test 

 how long various different seeds would bear immersion in sea- water without losing their 



1 The Asiatic species is distinct, see ante, p. 149. 



- Gardener's Chronicle, 1653, and Journ. Luta. Sue. LoiuL, i. p. 130. 



