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Messrs. F. L. Usher and J. H. Priestley. [Dec. 16, 



immediate and rapid decomposition set in, and a, gas was freely evolved, 

 which was found to be oxygen. The action proceeded as rapidly in the dark 

 as in the light. 



The following experiments were performed with the object of ascertaining 

 the nature of the catalyst : — 



(a) A plant was immersed in boiling water for :-30 seconds and was sub- 

 sequently found to be without action on hydrogen peroxide. 



(b) After treatment with dilute solutions of iodine, mercuric chloride, and 

 hydrogen sulphide, no action took place. 



(c) Some Elodea was suspended in air charged with chloroform vapour for 

 two hours in order to kill the protoplasm, and was then allowed to " recover " 

 for a similar period. Kapid disengagement of oxygen took place. 



(d) After immersion in very dilute formaldehyde solution, hydrogen 

 peroxide was not decomposed. 



These experiments seem to point to the existence of a catalysing enzyme. 

 Several attempts to extract it by simple maceration with water or salt 

 solution failed, and we were also unable to extract it after powdering leaves 

 in liquid air. Following a suggestion of Dr. Horace Brown, we ultimately 

 succeeded in obtaining it by previously drying a quantity of Ulodea, and 

 subsequently digesting with water at 30° for -18 hours. The enzyme was 

 precipitated by an excess of absolute alcohol and dried. 



By this process it is obtained as a light brown powder, containing diastase, 

 whose aqueous solution energetically decomposes hydrogen peroxide, whereas 

 ordinary malt diastase does not. Whether the enzyme is one already known, 

 or whether it is secreted specially for the purpose of catalysing hydrogen 

 peroxide, we cannot as yet say. 



On mounting a leaf of Elodea in very dilute hydrogen peroxide, and 

 examining microscopically under a high power, bubbles of gas were seen 

 to emerge from the chloroplasts only, an observation which shows the strict 

 localization of this enzyme to the seat of the photosynthetic process. 



In regard to the distribution of this enzyme, we have examined the 

 foliage leaves of plants belonging to 46 Natural Orders and representative 

 of the Vascular Cryptogams and all the main groups of the Phanerogams, 

 and have found the power of catalysing hydrogen peroxide in every case, 

 though the energy of the decomposition varies considerably in different 

 groups. It also occurs in etiolated leaves and in potato tubers, and, in fact, 

 appears to be associated with amyloplasts, whether possessing chlorophyll 

 or not. 



The Production of Formaldehyde and the Manner of its Removal. — It has 

 been found in the case of Spirogyra that starch appears in a previously 



