NO. 23 STIMULATION OF ALGAE BY ULTRAVIOLET MEIER 1/ 



APPEARANCE OF THE CELLS 



The lengths and the widths of 20 cells in each culture were measured 

 with an ocular micrometer. From these data the means of the measure- 

 ments of 100 cells from the most highly stimulated cultures and of 

 100 cells from the corresponding controls were computed and the 

 results tabulated in table 10. The measurements of the stimulated 

 cultures under 2352 A. are from the cultures exposed to that wave 

 length for 12 minutes, the set under 2483 A. from those with 30 

 seconds' exposure, the set under 2652 A. from those with 30 and 40 

 seconds' exposure, and the set of measurements under 2967 A. from 

 those with 133 and 200 seconds' exposure. The ratios were computed 

 by dividing the mean length of the measurements for 100 cells of 

 the stimulated cultures by the mean length for 100 cells of the controls. 

 The ratios for the width were obtained in a similar manner. 



Table 10. — Cell Measurements 1 



1 The mean is of 100 cells in each case from representative cultures. 



A study of the tables shows that the cells in the stimulated cultures 

 are shorter and wider than those in the control cultures. This is to 

 be expected as the rate of the multiplication of the stimulated cultures 

 is so much higher than that of the control cultures that the stimulated 

 cells probably do not have time to attain the length found under normal 

 conditions before they divide to form new cells. 



Plates 3 and 4 show photomicrographs of cells from stimulated 

 cultures and their corresponding controls made 2 years after inocula- 

 tion and irradiation. The cells of the stimulated cultures are darker 

 than those of the controls due to the greener appearance of the chloro- 

 phyll. They are also shorter and wider than the cells of the controls. 

 More dead discolored cells are present in the control cultures than in 

 the stimulated cultures. 



CONCLUSIONS 



A stimulative action causing increased cell multiplication of the 

 green alga Stichococcus bacillaris Naeg. has been found to result 



