204 Scientific Proceedings, Royal Dublin Society. 



Plmophycean Pig men ts. 



With a view to obtainiug colourless material on which to try the enzyme 

 reactions, some experiments were made on the pigments derived from this 

 group. A remarkable change from brown to green occurs when Fucus, 

 Ascophyllum, or other brown algse are boiled or steamed. This has long been 

 known and has been examined in detail in recent yeai's by Molisch (6, 7), and 

 Tswett (9, 10). They, in common with previous investigators, regard the water- 

 soluble brown pigment of the Pheeophycese as due to post-mortem oxidations. 

 It is easy to satisfy one's self that it is not due to an enzyme action, for Fucus, 

 Ascophyllum, Pelvetia, and Halidrys acquire a dark brown colour when 

 allowed to stand in air after having been boiled. This water-soluble brown 

 pigment is termed " phycophsein." Molisch reserves the term " phseophyll" 

 for a brown pigment occurring naturally, but not soluble in water. By 

 reduction or other change taking place in its molecules a green pigment 

 similar to chlorophyll is produced. This Molisch regards as the cause of 

 the colour change which occurs, as I have myself observed, not only upon 

 boiling, but when the protoplasm is made permeable by immersion in 

 ethyl or amyl alcohol. That it is not due to an extraction of pigment 

 is clear, for the alcohols remain untinged for a long time after the 

 change is complete. Tswett, too, has carried out an elaborate investigation 

 upon tliese pigments. He ascribes the natural colour to the mixture of 

 elilorophyll a and y, fucoxantliin, carotin, and fucoxanthophyll, and 

 attributes the appearance of green to the solution or destruction of 

 fucoxantliin which is red-brown in the solid state, but yellow in solution. 

 There does not, however, seem to be evidence that this pigment exists in the 

 plastids in the solid condition. I venture to suggest that this change on 

 boiling may be explained at least equally well as follows : Water-soluble 

 phycophsein is produced after death ; so it seems reasonable to suppose that it 

 is produced in the plastids of the superficial tissues during life. When the 

 protoplasm is made permeable, by boiling or treatment with hormones 

 such as the alcohols, reducing substances in the same or neighbouring cells 

 interact with this phyeophaein, converting it into a colourless body. Kylin (5) 

 has this year brought forward evidence tliat phycophsein is nothing but 

 oxidized fucosan. Fucosan he regards as a tanuiu-like substance, though not 

 a typical tannin. Tlius it it is quite possible that fucosan, like tannin, 

 may be an inliibitor of oxydase action. Again, it may be that during life the 

 oxidation of fucosan is a method by which these algse store a supply of 

 oxygen when it is abundant, as, for instance, during low water ; this being 

 given up if required when the supply is diminished by the returning tide. 



