Atkins — Oxydases and their Inhibitors in Plant Tissues. 206 



As is well known, acids only slightly decrease the depth of coloration of 

 phyeoplisein solutions ; but I have observed that, making use of an extract of 

 Halidrys siUqiiosn, the addition of a little zinc dust to the acid solution 

 results in the rapid reduction of the pigment to a colourless substance, 

 leaving only a pale yellowish solution. Treatment of the red-brown extract 

 with slightly acid hydrogen peroxide results in the destruction of the 

 pigment, with tlie production of a pale yellow, indistinguishable from tliat 

 given by the action of nascent hydrogen in the zinc dust experiment already 

 described. Here the peroxide is probably functioning as a reducing agent, 

 as it does with silver hydroxide and in the well-known method for reducing 

 a ferricyanide. In other recent papers Kylin (3, 4) maintains that Fueoidese 

 contain chlorophyll, carotin, xanthophyll, and phycoxanthin, but does not 

 satisfactorily explain the death-cliange from brown to green. That this is a 

 reduction, changing a brown " phaeophyll " to a chlorophyll, is the view put 

 forward by Molisch. Tiiat the change is a reduction appears to me to be 

 very probable, but that the resulting body is chlorophyll seems to be in need 

 of definite proof. That the coloured substance is phycophseiu, shown by Kylin 

 to be an oxidation product of fucosan, and only formed in small quantities 

 during life, is in my opinion quite as reasonable a view as that of Molisch, 

 though equally in need of direct proof. 



Rhodophycean Pigments. 



To satisfactorily examine the oxydase contents of the superficial cells, it 

 is necessary to remove tlie pigments. My attempts in this line are as yet 

 only of a preliminary nature ; but it was observed that the red pigment in 

 Plocamium coccineum, Rhodymenia palmata, and Gracilaria multipartita was 

 decolorized by alkalis, the green having been dissolved out by alcohol. 

 Addition of acids, sulphuric or acetic, restored the colour, but it was of a 

 slightly more purple shade than the original pigment. It was further 

 noticed that boiling for a minute sufficed to destroy the natural red colour, 

 but that addition of an acid again restored it. This looks as if the acid, in 

 this case, hydrolyzed a chromogen to produce an indicator-like body, whereas 

 with alkalis the pigment may merely form a colourless salt. 



Summary. 



1. Catalase was found in all the species tested, being very active in 

 some. 



2. Out of a total of twenty-nine, one alga gave the direct oxydase 

 reaction with guaiacum, whilst six gave the indirect — namely, on addition 



