94 Pflanzenchemie. 



cells of stomata and the celis abutting them are very rieh in epider- 

 mal oxidase, while the abutting cells may also contain the bündle 

 oxidase of Keeble and Armstrong. The leaf saps of /r;s^^rwßmc« 

 and Aspidium filix-mas contain powerful reducing substances which 

 inhibit oxidase reactions. Precipitation of the enzymes by alcohoi or 

 removal of the reducing substance by dialysis permits of the detection 

 of oxidase. The colours of the perianth of Iris are due to the 

 presence of a yellow plastid pigment or of a purple anthoc\'an 

 chromogen which arises by the action of the epidermal peroxidase on 

 a chromogen. The reducing substance may inhibit colour production. 



Part II p. 157 — 165. 1914. The leaves and flowers of Iris gave 

 the indirect oxidase reaction throughout, though not in many cases 

 until after the removal of the Inhibitors by means of hydrogen 

 Cyanide. Prolonged darkness has no decided effect on the distribution 

 of enzyme or Inhibitor. The occurrence of the natural sap pigments 

 in the flowers of about thirty species of Iris has been correlated 

 with the presence of oxidase and Inhibitor 



Part. III. The localisation of oxidases and catalases in some 

 marine algae. I.e. XIV, p. 199—206. 1914. Catalase was found in all 

 the algae tested. Out of a total of 29 species, only 1 gave the direct 

 oxidase reaction, while 6 gave the indirect reaction with guiacum. 

 In two cases only was a colour produeed with «naphthol. 



F. Cavers. 



Davis, W. A. and A. J. Daish. A stud}^ ofthe methods of 

 estimation of carbohydrates, especially in plant 

 extracts. (Journ. Agric. Sei. V. p. 437—468. 1914.) 



The authors deal with certain sources of error encountered in 

 estimating sugars in plant extracts. Large errors in the gravimetric 

 method may be obtained unless special care be taken in purifying 

 the asbestos used by boiling for at least 30 minutes with strong 

 causlic soda Solution. Weighing the reduced copper as cuprous oxide 

 may give rise to large error, and a process of weighing as cupric 

 oxide is described. The authors have studied the Volumetrie methods 

 of Ling and of ßertrand, and consider the former as preferable 

 in all respects. Owing to the accumulation of sodium acetate in 

 extracts, Inversion by citric acid of lower strength than 10 "/q is 

 ineomplete, but inversion by invertase is not interfered with by 

 this Salt, To estimate eäne sugar, both methods of inversion are 

 recommended; no loss of sugar oceurs, the loss stated by some 

 writers to take place is due to ineomplete inversion caused by 

 presence of sodium acetate. The action of dilute hydrochlorie acid 

 on different sugars is studied, and it seems impossible completely 

 to hydrolyse maltose at 70° or 100° without simultaneously destroying 

 large quantities of iaevulose or dextrose; the only available method 

 for accurate estimation of maltose consists in employing yeasts free 

 from maltase, introducing a correction (for pentoses, etc.) obtained 

 by fermentation with baker's or brewer's 5^east. A scheme is given 

 for the quantitative estimation of sugars in plant material. 



F, Cavers. 



Ewart, A. J., A comparative study ofoxidation by cata- 

 lysts of organic and inorganic origin. (Proc. Ro5^ Soe. 

 Lond. B. LXXXVIII. p. 284—320. 1914.) 



The author objects to the use of such terms as peroxidase, 



