Bd. XCVI. Nr. 21. XXV. Jahrgang. 



Botanisches Centralblatt 



Referirendes Organ 



der 



Association Internationale des Botanistes 



für das Gesammtgebiet der Botanik. 



Herausgegeben unter der Leitung 

 des Präsidenten: des Vice-Präsidenten: des Secretärs: 



Prof. Dr. K. Goebel. Prof. Dr. F. 0. Bower. Dr. J. P. Lotsy. 



und der Redactions-Commissions- Mitglieder : 



Prof. Dr. Ch. FSahauit und Or, Wsn. Trelease. 



von zahlreichen Specialredacteuren in den verschiedenen Ländern. 

 Dr. J. P. LotSy, Chefredacteur 



No. 47. 



Abonnement für das halbe Jahr 14 Mark 



durch alle Buchhandlungen und Postanstalten. 



3004, 



Alle für die Redaction bestimmten Sendungen sind zu richten an Herrn 

 Dr. J. P. LOTSY, Chefredacteur, Leiden (Holland), Rijn-en Schiekade 113. 



Timiriazeff. C, The Cosmicai Function of the Green 

 Plant. (Proc. Roy. Soc. London 1903. p. 421—461.) 



Formerly owing to the work of Drap er the photosyn- 

 thetic process taking place in the green leaf under the influence 

 of light was regarded as a funetion of its luminosity. But as 

 the author points out, light, in the narrow aeeeptance of the 

 term, does not exist so far as the plant is concerned. Drap er 's 

 spectrum was highly impure since he used a circular aperture 

 and this explains the eoineidence of the maximum chemical 

 effect with the maximum luminosity in the yellow and green, 

 this part of the spectrum being practically white tinged by 

 these colours. Timiriazeff showed that eoineidence of 

 chemical effect with Fr au n ho f er 's luminosity curve was out 

 of the question, but that a deeided relation to the energy-curve 

 exists. But the maximum energy was then thought to lie in the 

 infra-red and Cailletet showed that rays of light filtered through 

 a Solution of iodine in carbon bisulphide could not produce 

 reduetion of carbon dioxide in the green leaf. Herschel's 

 Law, which states that a photochemical reaction may be indu- 

 ced by those rays only that are absorbed by the substance 

 undergoing change — in this case the rays absorbed by the 

 green leaf ■ was then appealed to, and by exceedingly careful 

 and aecurate work the author has confirmed Herschel's 

 Law for this case — the assimilation curve reproducing 

 very nearly the absorption curve so far as the less refran- 

 gible portion of the spectrum is concerned. The secondary 

 maxima of absorption seem to have no effect. 1t is however 



Botan. Centralbl. Bd. XCVI. 1904, 34 



