NO. II 



PHOTOTROPIC SENSITIVITY JOHNSTON 



Bachmann and Bergann ( 1930) review the early work of Blaauw 

 and correct the energy values of his data for light absorbed by CUSO4 

 and water filter, surface reflections, and color filter in order to com- 

 pare his results with those obtained by Bergann. The results of Sonne 

 and Koningsberger are also corrected and compared. These data are 

 represented gra])hically in figure i, in which the continuous line is 

 the sensitivity curve. The data from Blaauw's work are indicated as 



360 380 400 420 440 460 480 500 520 540 560 580 600 620 

 Wdvc -length -nyi 



Fig. 2. — Graphs from Castle showing the relative efficiencies of different wave 

 lengths in their stimulation on Phycomyccs blakcsleaniis (horizontal lines), on 

 Phycomyccs nitcns from data of Blaauw (solid circles), and on Pilobolus calcu- 

 lated from data of Parr (open circles). 



small crosses, those of Sonne as circles, and those of Koningsberger 

 as horizontal lines. The multiplier for Blaauw's data in the short- 

 wave-length region is 2.5. 



From this work it is concluded that there are two maxima in the 

 phototropic curve and that these correspond in general to the maxi- 

 mum light absorption regions of chromolipoids. It appears that the 

 phototropic curvatures in the diff'erent wave-length regions follow the 

 absorption of light by specific substances or their compounds in these 

 same regions. 



The sensitivity of the sporangiophores of Phycomyces to light of 

 different wave lengths was investigated by Castle (1931). The 



