Physiologie. 3 



the soil. Correlated with the results of the previous paper, the 

 author emphasises the Controlling influenae of COo in the biology 

 of seeds, and suggests that the normal resting stage of a seed is 

 primarily a phase of narcosis. F. Cavers. 



Molisch, H., Ueber die Herstellung von Photographien 

 in einem Laubblatte. (Sitzber. kais. Akad. Wiss. Wien. Math, 

 nat. Kl. 1914. 2 pp. 1914.) 



Der Verf. hat gefunden, dass man in einem Laubblatte mit 

 Hilfe der Jodstärkereaktion deutliche Photographien beziehungsweise 

 Kopien von solchen erzeugen kann. 



Wird ein vollständig entstärktes Blatt von Tropaeolum majus 

 mit einem kontrastreichen Negativ bedeckt, an einem klaren sonni- 

 gen Tag von morgens bis abends dem direkten Sonnenlicht ausge- 

 setzt und dann nach Wegschaffung des Chlorophylls der Jodprobe 

 unterworfen, so entsteht im Laubblatt das Positiv des angewandten 

 Negativs. Auf diese Weise konnten z. B. die Photographien ver- 

 schiedener Personen im Blatte erzeugt werden. 



Das Blatt übernimmt in diesen Versuchen bis zu einem gewis- 

 sen Grade die Rolle einer photographischen Platte, beziehungsweise 

 eines Kopierpapiers. Dem Silbersalz der photographischen Platte 

 entspricht gewissermassen im Blatte der Chlorophyllapparat, dem 

 Silberkorn das Stärkekorn und dem Entwickler die Jodstärkeprobe. 



Molisch. 



Stiles, W. and I. Jöpgensen. The measurement ofelectri- 

 cal conductivity as a method ofinvestigation in plant 

 physiology. (New Phytol. XIII. p. 226—242. 5 figs. 1914.) 



A summary of work that has been done in the use of electrical 

 conductivity phenomena as a means of attacking various problems 

 in plant physiology. The authors bring together the very scattered 

 literature of the subject, call attention to the fact that the ränge of 

 methods available is much wider than is generally supposed, and 

 discuss the methods used and their advantages and drawbacks. In 

 discussing conductivity measurements outside living tissues, they 

 emphasise the necessity of rendering the cell membranes comple- 

 tely permeable in order to obtain an extract really representing the 

 cell sap The greater part of the paper is devoted to descriptions 

 of the methods used, and in concluding the authors State that though 

 the use of these methods in plant physiology is still only in its 

 preliminary experimental stage the results so far obtained render 

 it probable that with further development of methods electrical 

 conductivity will afford a convenient ad relatively simple means of 

 investigating certain groups of physiological problems. 



F. Cavers. 



Wager, H., Actio n oflight on Chlorophyll. (Proc. Roy. Soc. 

 Lond. LXXXVII. B. p. 386-407. 1914.) 



When Chlorophyll is decomposed by light, at least two distinct 

 substances are formed, one of which is an aldehyde or mixture of 

 aldehydes, and the other an oxidising agent capable of causing 

 liberation of iodine from potassium iodide. The decomposition of 

 Chlorophyll appears to be due directly to the action of light and is 

 not an after effect of photosynthesis. It occurs only in presence of 



