NO. 6 EFFECTS OF LIGHT ON ALGAE MEIER I9 



other ranges of wave lengths show different results. Some appear to 

 inhihit multiplication, while others seem greatly to enhance it. 



Inasmuch as the results depend on difference computations as be- 

 tween determinations themselves of considerable probable error, these 

 estimates of the effectiveness of different narrow ranges of wave 

 lengths to promote algal multiplication are very uncertain, but are 

 given for what they may be worth. 



Growth experiments made with definite narrow ranges of wave 

 lengths by the aid of Christiansen filters should give more conclusive 

 results. 



GENERAL CONCLUSIONS 



Multiplication of the unicellular green alga, Siiclwcocciis hacillaris 

 Naegeli, is proportional to the intensity of illumination ranging from 

 3.76 to 34.1 microwatts/mm-. A higher intensity than 34.1 micro- 

 watts/mm - such as 102.0 microwatts/mm - checks the growth of this 

 alga. 



Complex beams of radiation from 11 short wave length cut-off 

 filters were used to transmit progressively shorter and shorter wave 

 lengths from one transmitting only deep red, 6000 A, to the other 

 extreme, 3700 A, where most of the visible region is included. 

 Chlorophyll was formed under all the filters, but in best condition 

 when the wave lengths of the blue-violet region were included. 



A multiplication of algae ranging from twofold to fourfold was 

 obtained in the cultures. By computing growth ratios for many nar- 

 row ranges of wave lengths and by estimating approximate values 

 under the energy curves of the effective wave lengths it is found 

 that a wide red and infrared complex of waves from 0.6 to 1.4 

 microns is moderately eft'ective for the multiplication of the algal 

 cells. 



Some ranges of wave lengths appear to inhibit cell multiplication 

 and chlorophyll formation. Some appear to favor them. Only by 

 means of experimentation with isolated narrow ranges of light can 

 the effectiveness of all the wave lengths be determined. A similar 

 experiment with Christiansen filters instead of the glass ones is now 

 in progress and should give more conclusive results. 



