CHEMICAL AND PHYSIOLOGICAL STUDIES. 



183 



small strip, with an opaque sheath of tinfoil. Upon the uncovered 

 strip a small spectrum of sunlight is thrown by means of a suitably 

 arranged prism, and the whole left for some hours. The leaf is 

 then cut off and immersed in alcohol, to dissolve out the chloro- 

 phyll, and subsequently washed in distilled water and transfeiTed 

 for a time to a vessel containing a solution of iodine in potas- 

 sium iodide. It will then be found upon examining the leaf 

 after again washing, that in the part which was illuminated by 

 the spectrum a band of "stained" starch is present, the staining 



Fig. 115. — (a) Enoelmann's Bactebia Experiment. — S, Glass slide 

 (opacxue) ; K, Y, V, three spaces left clear, which are illuminated by 

 red, yellow, and violet rays respectively ; /, filament of Spirogyra. 



(6) Timiriazbff's Experiment. — L, Beam of white light ; P, prism ; 

 R, V, spectrum thrown upon a leaf. 



being deepest in that part which was previously illuminated by 

 the red rays, and weakest at the opposite or violet end. 

 Photosynthesis (followed by storing of starch) is thus more 

 intense under the influence of rays of low refrangibility. 



These two experiments show conclusively that assimilation of 



