NO. 6 EFFECTS OF LIGHT ON ALGAE MEIER 9 



the algal suspensions were practically colorless in appearance, but by 

 microscopic examination some green cells mixed with numerous 

 colorless cells were found for the following eight varieties : Sticho- 

 coccus hacillaris, Chlorella vulgaris, Scenedcsums chlorelloidcs var., 

 Oocyst is nacgdii, Chlorella viscosa, Scenedcsums Havescens, Cysto- 

 coccus irregularis and Pahuellococcus variegafus. All colorless cells 

 were found in the following four varieties : Palmellococctis proto- 

 thecoides, Coccouiyxa simplex. Chlorella vulgaris var., and Chlaruy- 

 domonas intermedia. 



THIRD EXPERIMENT 



In the third experiment, which was in progress from October lo 

 to November 9, 193 1, all the cultures in the four baths were con- 

 stantly agitated and lighted continuously. JMazda daylight lamps were 

 used and were so placed that the ratios of intensities in the four baths 

 were 1:3:9: 27. 



" The distance was measured from the glass bottom of the bath to the top of the filament 

 of the lamp. 



•> As measured with a thermocouple. 



In addition to the algae listed in the second experiment, cultures of 

 Haeinafoeoecus pluvialis and Pahuellococcus luiiiiafus were used. 

 Microscopic counts were made of each culture at the beginning and 

 atvthe end of the experiment. 



The increase in number of cells was roughly proportional to the 

 increase in light intensity in«the cultures of Oocysfis uaegelii. Pahnel- 

 lococcus protothecoides, Chlorella vulgaris, Pahuellococcus miniatus, 

 Chlainydoiuouas iuteriiiedia, Sceuedesuius chlorelloidcs var., Hetero- 

 coccus viridis, Chlorella viscosa. Cystocoecus irregularis, Cxsfococcus 

 cohaerens, Coccouiyxa simplex, and Pahuellococcus variegafus. Four 

 algae behaved diiferently. The most intense light caused the poorest 

 development of StieJiococcus hacillaris and Sceuedesuius Havescens. 

 although for the three other intensities the growth was proportional. 

 The growth was inversely proportional to the light intensity in 

 Chlorella vulgaris var. Chlorococcuui viscosum grew very little in all 

 four light intensities. Cells with green chloroplasts were present in 

 all the cultures of the algae listed above. Hematococcus pluvialis had 

 a few gray-green cells in the lowest light intensity, more green cells 



