178 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



between the Arctic Sea and the West Indies, and between 

 the Arctic Sea and Australia, though of course, as the 

 tables show, not the same genera. It will also be seen that 

 the comparison of the West Indies with Australia alone 

 shows a preponderance of specific over generic types in 

 common (except in the case of the item Protophycese the 

 least worked out group). This naturally shows a greater 

 affinity between these floras, as was indeed to be expected, 

 and it remains true when we substitute my previous lower 

 estimate of 116 for 135 species. I have elsewhere re- 

 marked on the relationship of these floras so far removed 

 from each other and on the fact that there is a greater 

 correspondence between them than between the West 

 Indian and the Indian ocean floras, though the generic 

 types of these latter correspond closely. This table of 

 figures speaks so plainly for itself that any discussion of it 

 would be a mere reiteration of its obvious statements. 

 I cannot help, however, calling attention to the totals of 

 forms common to all three regions, viz., Floridese, 17 gen- 

 era and only 5 species ; Phseophycese, 6 genera and only 

 one species (Eudesme virescens); Chlorophycese, 5 genera 

 and 6 species (four of which are notoriously cosmopolitan 

 Ulvacese — plants which do their best if I may say so to 

 become fresh water forms even, not content with a home 

 in the boundless ocean ; the one siphoneous alga is our 

 beautiful Bryopsis plumosa); and finally Protophycese, 4 

 genera and no species. 



It will be noticed also from a study of these totals that 

 while in the Arctic and Australian Eegions, the Phseo- 

 phycese far out-number the Chlorophycese, in the tropical 

 West Indian flora, the proportion is very markedly reversed 

 and the green Algse outnumber the olive brown. One is 

 tempted to put this down to the strong illumination of the 

 tropical sea but another reason is to be found in the fact 



