4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



APPARATUS AND TECHNIQUE 



The same metal table described by Meier (1934 b) was remodeled 

 and utilized for this experiment. (See pi. i.) This metal table is 

 constructed with four glass-bottomed water baths, each holding two 

 300 cc Erlenmeyer flasks. The four water baths are connected to a 

 centrally located thermostated mixing chamber which kept the tem- 

 perature at 19° C. In order to insure uniform dispersion of the 

 algal cells, a common driving mechanism continually agitates the 

 Erlenmeyer flasks. One of the cultures in each bath is illuminated 

 from below by monochromatic light from a light filter. Mazda pro- 

 jection lamps served as the source of illumination. The other culture 

 in each bath was contained in an Erlenmeyer flask which had been 



Table i. — Percentage Decrease in Intensity During Each Experimental 

 Period of 2 Weeks 



Experiments 



Filter 2 



Blue 



(4000-5200 A) 33.5 



Green 



(5000-5600 A) 50.0 



Yellow 



(5500-6200 A) 40.0 



Red 



(6000-7500 A) 28.0 



Infrared 

 (8500-12000 A) 



Note. — Intensity at beginning of each experiment was 19.5 to 

 each wave-length region. 



painted black to prevent the entrance of any light, thus providing 

 a check on the culture conditions in each bath. Each of the successful 

 experiments described here was run for a period of 2 weeks (April 

 9-23, May 7-21, and June 6-20, 1935), during which the temperature, 

 humidity, and light quality were maintained constant. The cultures 

 were given 12 hours of illumination daily, from 9: 30 a. m. to 9: 30 

 p. m. The cells in a drop of .01 cc volume obtained with the aid of 

 a specially calibrated pipette and a microscope slide marked in 2-mm 

 squares were counted microscopically for each culture at the beginning 

 and at the end of the experiment. Nephelometric measurements of 

 the increase of liquid turbidity as an indirect check upon the observed 

 multiplication of cells in each culture were also made as described by 

 Meier (1934 b). The light intensity was 19.5 to 20 microwatts/mm ' 

 for each wave-length region at the beginning of each experiment. 

 The intensity dropped during each experiment as recorded in table i. 



