GO 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



degree of probability that it would attain the highest, if not the 

 only maximum, under red glass. 



Spectrum ok the Adsorption-Bands of Chlorophyll. 



HO 



Red. Or. Yell. Green. 



Blue. 



Violet. 



A, B, C. &c., the principal Praunhofer's lines. I, II. Ill, &c.. the absorption-bands of 

 Chlorophyll. Rc't. orange, yellow, &c, indicate the approximate places of the different 

 coloured bands of the solar spectrum. 



With regard to transpiration, M. Wiesner and others have 

 come to the conclusion that it is just those rays which are 

 absorbed by chlorophyll which are most energetic in exciting 

 this function. According to my own experiments, however, this 

 general statement would seem to require some qualification ; 

 for, taking the means of numerous examples, I find that two 

 chief maxima occur in a very pronounced manner under red and 

 violet glasses, a minor one often occurring under green glass ; 

 while yellow, blue, and clear glasses as a rule give minima. 



With regard to assimilation, with which the experiments 

 discussed in this paper are concerned, M. Deherain* came to the 

 conclusion that it was the same chlorophyll absorption-bands 

 which were instrumental in exciting it, as with transpiration; so 

 that when the one function is stimulated to excess the other is 

 more or less deficient. My own experiments confirm this latter 

 statement, but do not seem to quite tally with the former ; for I 

 find that assimilation has maxima under yellow, blue, and clear 

 glasses. In other words, in a more or less degree of correspond- 

 ence with the position of absorption-bands alternating with 

 those required for transpiration, so that if the upper letters, 

 indicating the colours of the glasses, represent the positions of 

 maxima, and the lower ones those of minima, the two functions 

 may be illustrated as follows : — 



1 ranspiratwn ^ 

 Assimilation I 



K. 



Y. 

 Y. 



G. 



G. 



B. 



B. 



CI. 

 CI. 



V. (?) 



Ann. dns Sci. Nat. 5'"° Ser. (1839), 12, p. 5, 



