202 Scientific Proceedings^ Royal Dublin Society. 



Inspection of the table makes it at once apparent tliat the oxydases are 

 conspicuous by their absence, to judge from the reactions with a-naphthol 

 and guaiacum. Witli the former reagent, in two cases only, a slight 

 coloration was produced, though in both these the guaiacum blue was well 

 marked. With the latter, seven algae out of twenty-nine tested gave a 

 positive result, and in two of these the coloration was only feeble. The 

 behaviour of Furcellaria fadigiata is remarkable, for it alone gave the direct 

 reactions with guaiacum and benzidine. 



The benzidine reaction was always given, but only upon long standing in 

 the majority of cases, so that it appears rather to be due to spontaneous 

 oxidation than to enzyme action. This view is further borne out by tlie fact 

 that boiled specimens also darkened when in benzidine solutions. Yet it 

 seems to me that the depth of colour was not so great in the latter. Those 

 algae, however, which react with guaiacum also react rapidly with benzidine. 

 Work on Iris (1, 2) has, however, shown that tissues which, owing to the 

 presence of a reducing substance, fail to react with guaiacum or a-naphthol, 

 in many cases produce a colour with benzidine. With tlie algse there is a 

 further source of difficulty in the natural pigmentation, which renders such 

 reactions hard to observe. Microscopic sections do not in these cases afford 

 much additional information, for, as in Iris, it is quite possible that an 

 oxydase is active in the superficial, but not in the medullary tissue. An 

 attempt was made to remove inhibitors by immersion of the thallus of 

 Ascophyllum nodosum and of Polysiphonia fastigiata in 0'2 per cent, hydrogen 

 cyanide with subsequent thorough wasldng. After such treatment, catalase, 

 though strongly inhibited by the cyanide, as shown by Senter (8), was found 

 to be active. This proves that the washing was thorough. Sections of 

 Ascophyllum, however, gave no oxydase reactions ; and Polysiphonia when 

 macerated gave only a slight reaction with guaiacum, no more intense than 

 before the treatment. Thus, in the large majority of algse examined, there 

 is no decisive evidence of the existence of oxydases ; but, on the other hand, 

 reducing agents are present (as will be shown later) of such a nature as to 

 prevent the detection of the former by the usual methods. 



In this connection the case of Sphacdaria cirrhosa, one of the filamentous 

 Phseophycese, is of interest. Treatment with tlie benzidine reagent overnight 

 produced no browning, but the addition of hydrogen peroxide brought about a 

 rapid darkening, the colour being especially intense in the apical cells, by the 

 subdivision of which the thallus increases in length. This clearly is a case of 

 enzyme action, though no coloration was produced with a-naphthol, or even 

 with guaiacum, when the thallus was pounded up and tested. The cell-walls, 

 too, of this alga assumed a brown or delicate blue colour in the benzidine 



