434 



Prof. C. Timiriazeff. 



[Apr. 30, 



to the absorption bands of chlorophyll. In other words, a spectrum of 

 sufficient intensity, projected on a living leaf previously depleted of its 

 starch, will impress in this leaf an invisible image of the chlorophyll 

 absorption spectrum formed of starch grains. This latent image may 

 be developed by the iodine test. 



These previsions have been fully realised in the following experiment. 

 Healthy leaves attached to the living plant (a Hydrangea) but 

 previously deprived of their starch, after an exposure of 5 6 hours to 

 the influence of a small but very bright and pure spectrum, were 

 treated in the well-known way with an iodine solution. They 

 exhibited a well-defined spectrum of chlorophyll with its principal band 

 between B and C very prominent, and a gradual falling off towards 

 the blue end (fig. 5). Just as in the case of the reduction curve, no 

 secondary bands could be detected. 



FIG. 5. 



O.B.C. D. 





I. 2. 3. 4. 5. 



Photosynthesis of C 6 H 10 O 5 in the Spectrum. 



The blue and violet rays produced hardly any cftect. This last 

 result may be chiefly attributed to the fact that the appearance of 



