268 Phj'siologie. 



Affinität in eine Absorptionsreihe, es sind das die Chloroph^^lline 

 <« und ß und die Xantophylle «, «' und ß, ausserdem Carotin, das 

 im Lösungsmittel verbleibt. Die Chlorophj^lline sind die fluorescie- 

 renden Bestandteile des Blattgrüns; sie besitzen gut charakterisierte 

 Absorptionsspektren, die in ihrer Vereinigung das Spektrum des 

 Chlorophylls ergeben. In beiden Bestandteilen findet also eine op- 

 tische Arbeitsteilung für die C-Assimilation statt. Beobachtungen 

 im Reichert'schen Fluoreszenzmikroskop machen es wahrschein- 

 lich, dass sie auch im lebenden Chloroplasten eine Fluoreszenswir- 

 kung ausüben. G. Bredemann. 



Usher, F. L. and J. H. Priestley. The mechanism ofcar- 

 bon assimilation. (Proc. Roy. Soc. LXXXIV B. p. 101— 112. 1911.) 



The authors give details of further experiments supporting 

 conclusions arrived at in their earlier work, as to the primary pro- 

 ducts of photolytic reduction of aqueous Solution of carbon dioxide. 

 By the use of other sources of energy — 1) « and ß rays from 

 radium emanation and its products, 2) the radiation from a quartz 

 mercury vapour lamp — Solutions of carbon dioxide were decom- 

 posed with formation of formaldehyde and hydrogen peroxide. 

 Experiments with Chlorophyll films are described, leading to the 

 conclusion that the bleaching of Chlorophyll in sunlight, whether 

 carbon dioxide is present or not, is due to formation of hydrogen 

 peroxide; while further experiments showed that oxygen is evolved 

 from green tissues in which the catalase was not killed, and from 

 gelatin films containing catalase and covered with a film of Chloro- 

 phyll on being exposed to light in air containing carbon dioxide. 

 Further evidencc that some of the energy supplied to a film of 

 Chlorophyll by sunlight is used in the photolytic reduction of carbon 

 dioxide was obtained by an experimental proof that such a film in 

 sunlight in presence of carbon dioxide is at a lower temperature 

 than a similar film also in sunlight but in air free from carbon dioxide. 



F. Cavers (London). 



Wheldale, M., On the direct guiacum reaction given by 

 plant extracts. (Proc. Roy. Soc. LXXXIV B. p. 121 — 124. 1911.) 



Previous work on oxidising enzymes has led to the Interpre- 

 tation of the direct blueing action on guiacum in terms of the acti- 

 vity of a System consisting of an organic peroxide in conjunction 

 with a Peroxydase. The author finds that the power to give the 

 direct action possessed by watery extracts of tissues is accompanied 

 by the formation of brown pigments in the tissues on exposure to 

 Chloroform vapour. When the direct action is not given, the extract 

 will blue guiacum on addition of hydrogen peroxide (indirect 

 action), and the tissues do not show change of colour in Chloroform 

 vapour in the same period of time. The direct blueing of guiacum 

 is considered to be due to the presence of the dihydric phenol 

 pyrocatechin in the plants; the pyrocatechin is oxidised on the 

 death of the tissues and then acts as a peroxide, enabling the per- 

 oxidase almost universally present to transfer oxygen to the guiacum. 

 Hence the direct guiacum reaction has probably no real significance 

 as such in plant metabolism, but is merely the outcome of the pre- 

 sence of a certain metabolic product. F. Cavers (London). 



