Laing. — On the Alga 1 of New Zealand. 313 



other method of distribution besides those already referred to 

 that occurs to me as being worthy of mention is that by 

 means of sea-birds. 



It is by the agency of these that Sir Joseph Hooker 

 endeavours to account for the existence of the phanerogamic 

 flora of Kerguelen's Land,* but it is practically hopeless to 

 account for the distribution of our seaweeds by any such 

 method. Many of them live below low-tide mark, and so 

 would scarcely be likely to be picked up by birds except as 

 drift-weed. Some of these with anomalous distribution are ex- 

 tremely delicate and very small — e.g., Polysiphonia ceratoclada, 

 which grows to a length of 15mm. or 20mm., and is less 

 than lmm. in diameter. It is. however, a very distinct and 

 recognizable species. It is common in New Zealand, and has 

 been reported from Amsterdam and St. Paul Islands. Such 

 a distribution could scarcely have been effected by sea-birds. 

 Still, this is a single extreme case, and of itself does not dis- 

 prove or prove anything. It is merely to be taken as a typical 

 example of the difficulties to be met with, and is only to be 

 regarded in conjunction with other facts. If, again, sea-birds 

 have been distributing-agents, why should they have carried 

 so many Fuegian and New Zealand forms to Kerguelen and 

 Tasmania, but not to South Africa and southern Australia? 

 Whatever may have been their work in distributing land- 

 plants, I think that they may have been practically left out of 

 consideration as distributors of the Algae. If this is so, then 

 the discussion is somewhat narrowed down ; and it may be 

 possible to get from the Algse more definite evidence upon 

 various questions of distribution than is obtainable from the 

 flowering plants. 



We have now to refer to the action of ocean-currents. I 

 have already shown that in many cases these have been 

 unable to establish a species on the further side of a compara- 

 tively narrow ocean - barrier, even when similar conditions 

 appear to exist in both localities. Sir J. Hooker, however 

 (loc. cit.), states that " oceanic currents have doubtless brought 

 the marine Algse to Kerguelen Land." This may be true for 

 the majority of them, but I cannot think that it Is true for all. 

 For example, under this hypothesis, why should Adenocystis 

 lessonii, Polysiphonia abscissa, Nitophyllum multinerve, and 

 several other species have drifted from Fuegia to Kerguelen, 

 but not from Tasmania to Australia ? or how did Galopliyllis 

 hombroniana, Antithamnion ptilota, and two or three other 

 species reach the antarctic islands from New Zealand without 

 establishing themselves at intermediate points? Whatever 

 may have been the centre of distribution, we cannot account 



* Phil. Trans. Roy. Soc, vol. clxviii., p. 13. 



