§3] 



EFFECT UPON GENERAL FUNCTIONS 



169 



close to the absorption band of clilorophyll. Observations 

 ■upon the chlorophylls of brown, blue-green, and red cells, 

 which, as Engelmann's microspectro-photometer indicated, 

 have a maximum absorption at other points, showed a maxi- 

 mum of assimilative activity at these other absorption points. 

 In bacterio-purpurin also, in which some of the most active 

 assimilative rays are those of the invisible red at about 

 X = 0.85 /x, most oxygen is produced at this point. (Engel- 

 MAKK, '83, p. 709.) 



Finally, by an ingeniously devised experiment, Timieiazeff 

 ('90) has settled this matter in the most direct and indubitable 



Fig. 46. — Piece of Cladophora with swarming Ijacteria in the microspectrum (gas- 

 light) . The chlorophyll grains which fill the cells very uniformly are omitted ; 

 and, instead, the absorption band between B and C, and the tolerably pro- 

 nounced band at the violet end between i' and F, are indicated by shading. 

 (From Engelmann, '82.) 



fashion. He kept a plant for two or three days in the dark, 

 until the starch in its leaves had gone; then, in a dark room, a 

 prismatic spectrum was thrown upon the leaf and the position 

 of Featjenhofer's lines indicated on the leaf. After from 

 three to six hours, starch had formed, under the influence of 

 the light, only in the region of the absorption bands of chloro- 

 phyll lying between B and D. This was determined by plung- 

 ing the leaf into boiling alcohol, thus decolorizing it, and then 

 staining in tincture of iodine, which combines especially with 

 the starch. The deeply dyed places, where starch had been 

 formed, reproduced the absorption spectra of chlorophyll. 



The concurrent testimony of these and other observers work- 

 ing upon so diverse material and with such excellent methods 



