87 



may be formed by photosynthesis and in the metabolism of the 

 plant. Heffter^^ believed that the so-called reducing enzymes 

 are not enzymes at all, but that the reducing action is due to the 

 decomposition products of protein, especially those containing 

 the SH group. This, however, is denied by Frankel and Dimitz'^* 

 who believe that the reducing power of cells is due to their 

 unsaturated fatty substances. 



It seems likely that the oxidizing ferments assist in carrying 

 on the oxidative processes of respiration by increasing the 

 rapidity of the combination of oxygen with the oxidizable sub- 

 stances in the plant. It has long been known that there are 

 certain plants which at times develop a temperature above that 

 of their surroundings, representatives of the Araceae showing 

 this peculiarity in a striking manner. Hahn^^ investigated this 

 phenomenon in Arum maculatum, the spadix of which is often 

 from 20° to 2^° C. warmer than the surrounding air. He used 

 press-sap from the spadix of the plant and found that upon ex- 

 posure to the air, the liquid rapidly became greenish black; so he 

 concluded that an oxidizing enzyme (tyrosinase) was present. 

 Hahn allowed the press-sap to remain at 25° for several days and 

 at the end of that time the content of sugars, originally high, 

 dropped to nothing, with accompanying loss of weight in the 

 carbon dioxide evolved. This process could be entirely pre- 

 vented by heating the press-sap to 60° for half an hour before 

 allowing it to stand. Furthermore, the same process took place 

 in an atmosphere of hydrogen ; so Hahn thought he was dealing 

 with a case of intra-molecular respiration carried on by oxidizing 

 enzymes. Krause^" noticed a similar elevated temperature with 

 loss of dry weight [probably carbohydrates] in Arum italicum 

 and Knoch^^ did so in the case of the flower of Victoria Regia 



"Heffter. Die reduzierenden Bestandtheile der Zellen. Med. Naturwiss. 

 Arch, i: part i, p. 15. 1907. 



38 Frankel and Dimitz. Gewebatmung durch Intermediarekorper. Wiener 

 klin. Wochensch. 1909: No. 51, p. 1777. 



^Hahn. Chemische Vorgange im zellfreien Gewebsaft von Arum maculatum. 

 Ber. Chem. Gesell. 33: 3555. 1901. 



^"Krause. Ueber die Bliitenwarme von Arum Italicum. Abhandl. Naturfor. 

 Gesell. zu Halle, 1882, p. 16. 



^iKnoch. Untersuchungen liber den Physiologie, etc., der Blute von Victoria 

 Regia. Diss. Marburg, 1897. 



