264 Physiologie. 



the amount of carbon dioxide in Solution undergone by the water 

 in passing over the plant is the measure of the respiration or assi- 

 milation that is taking place. For assimilation experiments the water 

 supplied can be enriched with any desired amount of carbon 

 dioxyde; the glass Chamber is sunk in a large copper water-bath 

 with a glass window, and the temperature and illumination can be 

 controlled. With vigorous assimilation much oxygen is given off as 

 bubbles, which take up an appreciable amount of carbon dioxide 

 from the Solution, hence this gas must be collected and measured 

 as a correction to the apparent diminution in the dissolved carbon 

 dioxide; the gas is separated from the water bj^ a valve at the 

 highest point of the apparatus, and collected automatically for ana- 

 lysis. The method described is free from the limitations of the 

 bubble-counting usually employed in the investigation of assimilation 

 in water-plants, and enables critical measurements to be made of 

 the assimilation throughout the whole ränge of the external factors 

 that primarily control this function. F. Cavers (London). 



Blackman, F. F. and A. M. Smith. On assimilation in sub- 

 merged water-plants and its relation to the concen- 

 tration of carbon dioxide and other factors. (Proc. Roy. 

 Soc. LXXXIII B. p. 389—412. 1911.) 



The aim of the experiments, carried out by a new method 

 which takes account of the alteration of the dissolved gases as Avell 

 as of the gases evolved as bubbles, was to demonstrate the nature 

 of the relation between assimilation and the chief environmental 

 factors: carbon dioxyde supply, light intensity, and temperature. The 

 relation is such that the magnitude of this function in everj^ com- 

 bination of these factors is determined by one or other of them 

 acting as a limiting factor. From the data obtained a new type of 

 diagram is constructed by which it is possible to foretell what 

 value of assimilation in Elodea will be attained in any combination 

 of medium magnitudes of the three factors; in this diagram, against 

 the different values of assimilation as ordinates, are ranged three 

 separate curves showing the degrees of carbon dioxide supply, tem- 

 perature, and illumination which are respectively essential for the 

 attainment of each value of assimilation. In the discussion, stress 

 is laid on the non-existence of true optima, and it is concluded that 

 the results of previous workers are more harmoniously interpreted 

 from the point of view of interacting limiting factors than by the 

 conception of optima. F. Cavers (London). 



Brudny, V., Eine Methode zur kontinuierlichen Rein- 

 zucht von Mikroorganismen. (Cent. Bakt. 2. XXXVI. p. 

 573—577. 1913.) 



Der Apparat soll das bei manchen Mikroorganismen notwen- 

 dige regelmässige Umimpfen vereinfachen; das wird dadurch er- 

 reicht, dass man sie annähernd 100 mal hintereinander mit neuer 

 Nährlösung versehen kann, ohne das ein Oefifnen des Apparates 

 notwendig wird. Der Apparat besteht aus 3 vor dem Gebrauch zu 

 sterilisierenden untereinander verbundenen Gefässen: einer grösse- 

 ren Flasche zur Aufnahme der sterilen Nährlösung, dem Kulturgefäss 

 und dem Sammelgefäss in das die verbrauchte Nährlösung mit 

 den betreffenden Mikroorganismen entfernt wird. Das Uebertreiben 



