CHAP, ii Photosynthesis 317 



maximum about the region F-G, but only a much smaller 

 one than the first-mentioned. He emphasized its occur- 

 rence in his paper of 1884. Pfeffer, using this method, 

 declared himself unable to convince himself of its existence 



(Phys., i. 334)- 



In his early work Timiriazeff investigated chiefly the red 

 end of the spectrum. His starch method seemed to indi- 

 cate an absence of activity in the blue. A few years later 

 he adopted a method devised by Dubosq to produce a pair 

 of complementary colours from the spectrum. He described 

 the apparatus as consisting of a cylindrical lens and of 

 a wedge-shaped prism fixed in a plate of glass, and said 

 that it gives, instead of a spectrum, two strips of light 

 of equal intensity and complementary colours, each strip 

 comprising the rays of half the spectrum. He could thus 

 compare the effect separately obtained of the two halves. 

 He was enabled to prove a maximum power in the blue 

 equal to about half the maximum in the red-yellow. 



Using this instrument, he was able to show a very pro- 

 minent effect by the iodine method, the amount of starch 

 not being, however, so large in the part illuminated by 

 blue rays as in that by the red and yellow part, of the 

 spectrum. 



Reinke's researches in 1884 and 1885 next call for com- 

 ment. He devised an instrument which he called a spectro- 

 phore, which enabled him to experiment with any part of 

 the spectrum he chose. The light was admitted from 

 a heliostat and conveyed by means of a lens to a prism, 

 and the resulting spectrum thrown upon a glass screen. 

 By means of two adjustable pieces of wood behind the 

 screen forming a kind of shutter, which could be adjusted 

 to give a slit of whatever width was desired, Reinke was 

 able to employ whatever part of the spectrum he wished. 

 Another lens placed in front of the shutter combined 

 the emergent rays into a beam of light which was 



