Laing. — On the Alga of New Zealand. 303 



those which are most serviceable to the plant in the decompo- 

 sition of carbon-dioxide ? The latter view has received the 

 most support. >:: The same question may be asked in a slightly 

 different form with regard to the phycoerythrin of the Floridece 

 and the phycophaein of the Phceojih/jcece. Do these pigments 

 act as a protection against the blue light of the sea, or do they 

 absorb special rays, and give them out with altered wave- 

 length, more suitable to the needs of the plant? It seems to 

 me that in the present state of our knowledge discussion of 

 the relative percentages in different districts of brown, red, 

 and green seaweeds will help us but little to a solution of our 

 difficulty, though perhaps the increase in the percentage of 

 green seaweeds towards the tropics is easier of explanation by 

 the theory of absorption and alteration of wave-length than 

 by the theoiy of protection. Data as to the depth to which 

 species attain in different localities, and as to the variation of 

 shade and tone with the depth, would probably be instructive. 



It may be worth while to put on record here that I have 

 observed in Ghampia novcz-zealandice a remarkable iridescence, 

 consisting chiefly of blue and green rays. When in the water 

 the plant in this respect reminds one strongly of the brilliant 

 iridescent elytra of certain beetles. On removing the specimen 

 from the water the iridescence to a large extent disappears, 

 and there is not a sign of it after the plant has been dried. 

 According to Kerner,f whose theories, if not always accurate, 

 are frequently remarkable, and very often suggestive : " Several 

 of the sea-inhabiting Floridece, and sea-wracks belonging to the 

 genera Plujllocladia, Polysiphonia, Wrangelia, and Cystoseira, 

 even exhibit under the water a peculiar luminosity which may 

 be compared with that of the luminous moss, although the 

 optical apparatus is here essentially different. In the super- 

 ficial cells of the luminous Phyllocladias are to be found plates 

 segregated out of the protoplasm and closely adhering to the 

 outer walls, which contain a large number of small, crowded 

 lenticular bodies. From these minute lenses the green and 

 blue rays are chiefly reflected, and thus the peculiar iridescence 

 is produced. But, on the other hand, yellow and red rays are 

 refracted on to the chlorophyll granules, and consequently 

 these plates must be regarded as an apparatus for focussing 

 the light, which, by its passage through the thick layers of 

 water, has undergone a considerable diminution." 



It will be interesting to examine our Ghampia and see if 

 any similar structure can be made out in it. I have not seen 

 the original paper which is Kerner's authority for his state- 

 ments. He also affirms in a short passage (loc. cit.) that may 



* " Physiology of Plants," p. 156 : S. H. Vines. 



t " The Natural History of Plants," English translation, p. 388. 



