PHOTOSYNTHESIS 209 



pound ; by losing a molecule of oxygen it might become 

 formaldehyde, afterwards converted by polymerisation 

 into grape sugar. 



Schmitz, in 1882, though he did not touch on the 

 physiological problems concerned, gave a very full 

 account of the structure and development of the chloro- 

 plasts, more especially of Algae. He expressed dissent 

 from the view that the plastid formed a reticulum, and 

 held that this was induced by the action of acids, and 

 that the pigment was diffused through a homogeneous 

 matrix. The chloroplasts, moreover, never arose de novo 

 from the protoplasm, but always as a consequence of the 

 division of pre-existing plastids. On this point he was 

 supported by Schimper, who published a paper on the 

 subject in the following year. 



Another contribution to the subject came from the 

 pen of Reinke in 1884, in which he discussed the much 

 debated question as to the relative efficiency of the 

 different rays of the spectrum in the exhalation of oxygen 

 from green cells. In this paper he described an apparatus 

 which he termed a spectrophore and which he employed 

 in his researches. A pencil of light from a heliostat is 

 projected through an objective on to a large prism, by 

 which the spectrum is thrown on a screen consisting 

 of two movable boards, arranged so as to leave a slit 

 between them. By manipulating the boards the slit 

 may be opened or reduced to any extent and any portion 

 of the spectrum allowed to pass through. The rays 

 selected fall on a biconvex lens behind the screen and are 

 focussed on the object to be examined. Thus light of 

 any colour or any combination of colours up to pure 

 white may be obtained by varying the aperture of the 

 slit. Reinke estimated the rate of exhalation of oxygen 

 by the old gas-bubble method, and from a large number 

 of experiments he concluded that the absolute maximum 

 of evolution of oxygen is effected by rays of wave-length 

 690-680, i.e. those between Fraunhofer's lines B and C. 



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