THE PLANT OXIDASES 235 



fastigiata gave the direct reaction, strongly with guaiacum 

 and benzidine, and feebly with a-naphthol. Delesseria 

 sanguinea also acted on all three reagents, but only after 

 the addition of peroxide. Of the others, only Laminaria 

 saccharina and L. digitata gave a well-marked blue colour 

 with guaiacum, upon the addition of peroxide, while slight 

 reactions were given by Cystoclonium purpurascens, 

 Gracilaria confervoides, and Polysiphonia fastigiata. All, 

 however, oxidized benzidine in presence of peroxide. 

 It is as yet uncertain whether this is in every instance due 

 to an enzyme, and it is especially produced in the walls 

 and mucilage for example, in the walls and cells of 

 Sphacelaria cirrhosa, and in the mucilage connecting the 

 cells of the diatoms Tabellaria and Pinnularia epiphytic 

 on Sphacellaria. In Ulva it was found that the blue 

 oxidation product of benzidine appeared in cell walls of 

 the decolorized thallus quite as rapidly in boiled as in 

 unboiled tissue. 



The presence of an inhibitor in these algae has already 

 been mentioned. Segers-Laureys (1914) too found a per- 

 oxidase in the mucilage of various brown algae. Duggar 

 and Davis (1914) also carried out an investigation as to 

 the absence of oxidizing enzymes in the cells of Fucus 

 vesiculosus. [See note, p. 250.] 



OXIDASE E/E AGENTS AND THEIR LIMITATIONS. 



In the course of this chapter, mention has been made 

 of the use of certain reagents for the detection of oxi- 

 dases. These are usually dissolved in alcohol, and the 

 solution is then diluted with water to such an extent that 

 the solute, present only in small quantities, is still held 

 in solution. This dilution is usually accomplished just 

 before applying the reagent, as oxidation by dissolved 

 oxygen takes place to a smaller extent in alcohol than in 



