304 Transactions. — Botany. 



be worthy of quotation as new to most of my readers that, 

 " If the barrel-shaped and spherical cell-structures connected 

 into chains, the cyst-like and berry-shaped outgrowths of the 

 unicellular Caulerpas and Halimedas . . . are accepted 

 as contrivances by which light is collected and focussed on 

 those places within the cells where chlorophyll bodies are 

 heaped up, then no mistake will be made." If there is any 

 truth in this statement our Lychate darwinii and Caulerpa 

 sedoides should serve excellently well to prove it. 



The next point to which I must draw your attention is the 

 proportion of species to the genus in our Algae. As we have 

 307 species distributed among 117 genera, it is evident that we 

 have just over two and a half species to the genus. According 

 to Mr. G. Murray,* " In the warm Atlantic the genus averages 

 well over five species ; in the Indian Ocean the proportion is 

 nearer four than three species to the genus ; while at the Cape 

 it is almost exactly three. This is instructive, when we 

 remember, as I have elsewhere! pointed out, that, while the 

 arctic Algae average slightly more than two species to the 

 genus, the West Indies and Australia average rather more than 

 five. I estimate that the north temperate Atlantic yields an 

 average of about four and a half species to the genus." 



Thus it appears we have only about half as many species to 

 the genus as Australia has, but, as there are apparently only 

 about three species to the genus at the Cape, it would probably 

 be too venturesome to say that the small proportion in New 

 Zealand is due to the fact that we are dealing with an insular 

 rather than with a continental flora. It must be noted, how- 

 ever, that the Algae of the Cape are probably not so well knovru 

 as those of New Zealand. On the other hand, as our coast- 

 line is varied in character, and extends through more than ten 

 degrees of latitude, we might have anticipated that those 

 genera which have obtained a footing here would have 

 developed many species, but this appears only to have been 

 the case in such genera as are variable elsewhere, — e.g., Poly- 

 siphonia, Gigartina, Delesseria, Cladophora. 



This leads us up to the question of the distribution of our 

 species. It may be as well to point out, for the help of the 

 general reader, that marine Algae are not so widely distributed 

 as might on first thoughts be imagined. Indeed, it might be 

 supposed that the only limitations to their distribution would 

 be due to unsuitable environment ; but this is by no means 

 the case. In spite of the great geological age of this class of 

 plants, and their marine habitat, many of them are local in 

 distribution. The deep sea is, generally speaking, a barrier 



* " Phycological Memoirs," part; ii., pp. G6, 67. 

 t Trans. Biol. Soc. Liverpool, vol. v., p. 77. 



