566 A NATURALIST IN THE PACIFIC 



Hawaii, and Tahiti, and by the former placed also in Ceylon. Hillebrand 

 and Seemann are followed by Drake del Castillo as regards the Tahitian 

 species. Taubert, in his monograph on the Leguminosae (Engler's Pflanz. 

 Fam., Teil 3, Abth. 3, 1894), takes the same view of the Polynesian 

 species and of its wide distribution. However, in the Genera Plantarum 

 and in the Index Kewensis, the Asiatic and Polynesian species have been 

 always kept apart. The two species of the genus mentioned in the 

 first work are increased to five in the Index Kewensis, viz., one in Fiji 

 (S. lucidum), one in Hawaii (S. ruber), two in Madagascar, and one in the 

 Philippines. 



NOTE 40 (page 88) 

 PRECAUTIONS IN TESTING SEED-BUOYANCY 



Many seeds and fruits require a few hours' soaking before they sink ; 

 and when small they will rest a long time on the surface of still water, but 

 a touch with the finger or a drop of water will send them to the bottom. 

 A few will float a few days (3 or 4) before sinking ; but such are included 

 in the non-buoyant group. Only in rare cases does prolonged drying 

 increase the period of flotation by more than a few days, examples being 

 given at the end of the Table of Buoyancy results under Note 10. Adherent 

 air-bubbles, a common cause of adventitious buoyancy, must always be 

 removed. 



NOTE 41 (page 91) 



THE BUOYANCY OF THE SEEDS OF CONVOLVULUS SOLDANELLA IN FRESH 

 WATER AND SEA-WATER COMPARED 



The experiments were commenced at the close of September, 1894, 

 and covered six months. At the end of this period in Mr. Millett's experi- 

 ment, 56 per cent, of the seeds were afloat in fresh water, and 62 per cent, 

 in sea-water ; whilst in my own experiment 7 2 per cent, floated in fresh 

 water, and 65 per cent, in sea-water. I was indebted to Mr. Millett's 

 courtesy for the seeds. 



NOTE 42 (page 96) 

 ON SECULAR CHANGES IN SEA-DENSITY 



Exact data bearing on this subject are not at my disposal ; but it would 

 seem that geologists have formed conflicting conclusions from similar 

 premises. There is the view that the composition of the ocean water was 

 very different in early geological periods (Encycl. Brit., x., 221); but I should 

 imagine that the character of the crustacean fauna of those seas would 

 negative any great divergence from the present condition. Suess implies 

 that the ancient seas carried the same minerals in solution that they do 

 now, and it is to be inferred in a similar proportion (E. de Margerie's 

 French edition of Das Antlitz der Erde, ii., 343 and 345) 



