302 Transactions. — Botany . 



done ; but I think we may assume that in most cases the 

 position of the species has been determined from its funda- 

 mental and not from its external characters. 



Perhaps the first thing to be now noticed is the numerical 

 proportions of the green, brown, and red seaweeds in our list. 

 They are respectively 24, 55, and 228. "Now," says Mr. G. 

 Murray,* " while in the arctic and Australian regions the 

 Plueopihyccce far outnumber the CJdoropJiycece, in the tropical 

 West Indian flora the proportion is very markedly reversed, 

 and the green Algae outnumber the olive-brown." One would 

 imagine at first sight that this was due to the stronger 

 illumination of the tropical seas ; but Mr. Murray believes 

 that the irruption of fresh water from the Orinoco and the 

 tideless character of the x\ntilles are probably largely con- 

 tributing agents to this result. Be this as it may, in New 

 Zealand the ChlorophycecB number only 44 per cent, of the 

 Phceophyccce ; in the neighbourhood of Port Phillip the per- 

 centage increases to 65 ; for the Cape of Good Hope it is 71 ; 

 and for the Indian Ocean it is 103 : in Great Britain it is 68. 

 There is here evidently a marked connection between the 

 latitude and the percentages given. It may, of course, be 

 objected that the area of the Port Phillip district is too small 

 to compare with the others. I chose it because there are 

 recent statistics! for it, and thorough collections have been 

 made from the locality. However, taking the most recent 

 numbers for the whole of Australia,! the percentage is 55. 

 This is probably too small, as many of the Glilorophycece are 

 minute, and would escape notice unless very close search were 

 made. It should also be remembered that the Algaj of 

 southern are very much better known than those of northern 

 Australia. On the other hand, it should be pointed out that 

 the figures as given in the " Flora Antarctica " and in Dickie's 

 list for Kerguelen Land§ show that in the antarctic district 

 the numbers are about equal. This unexpected preponderance 

 of green forms is to be accounted for, as will presently be seen, 

 by the strange absence of the Fucacece from the antarctic 

 flora. 



Of course, the importance of these figures is in their bearing 

 on the functions of the pigmentation of the Alg33 and of plants 

 in general, the question at issue being, Does the chlorophyll 

 act as a filter to allow only the useful rays of light to pass 

 through, or is it an absorbing agent, collecting and utilizing 



* Trans. Biol. Soc. Liverpool, vol. v., p. 178. 

 /'Catalogue of Marine Algse collected near Port Phillip Heads," by 

 J. Bracebridge Wilson, F.L.S. ("Proceedings of the Royal Society of 

 Victoria," vol. iv., part 2.) 



\ "Journal of Botany," July, 1893, p. 210. 



§ Phil. Trans. Roy. Soc, vol. clxviii. 



