NO. ly GROWTH OF ALGAE IN WAVE-LENGTH REGIONS MEIER 3 



were observed in the specimens exposed for 24 hours to the green 

 (4968-4916 A), violet (4078-3821 A), or ultraviolet (3028-2054 A). 



Johnston (1932) discusses at length the effect of infrared on the 

 growth of plants as observed in his own experiments in addition to 

 the conclusions formulated by other investigators. In general, it is 

 agreed that if not actually destructive, the infrared region of the 

 spectrum is of little or no benefit to chlorophyll formation. Burns 

 (1933) also found infrared radiation detrimental to photosynthesis. 



There exists considerable difference of opinion regarding the effec- 

 tiveness of the various wave lengths. Warburg and Negelein (1923) 

 have found the maximum chlorophyll assimilation of Chlorella vul- 

 garis to be in the red (6100-6900 A), with a minimum in the blue 

 (4360 A). Gabrielson (1935) also found assimilation in Sinapsis 

 alba to be greatest in red-Orange light and least in the blue-violet. 

 Dangeard (1927), using Wratten filters, found that growth and mul- 

 tiplication of green algae, blue-green algae, and diatoms takes place 

 only in red-orange light, the other radiations affecting the plants as if 

 they were in complete darkness. 



Numerous other scientists could be cited whose work gives rather 

 contradictory results. The fact that careful scientific workers have pro- 

 duced contradictory evidence that leads to uncertainties emphasizes 

 the need for precise cjuantitative work with isolated narrow wave 

 length bands of light. 



THE PLANT STUDIED 



The unicellular green alga SticJwcoccits hacillaris Naegeli has an 

 elongated cell usually varying from 2 to 2.5 /a in diameter and 4 to 

 8 fxin length. Multiplication takes place by transverse division of the 

 protoplast which partially fills the cell and the formation of cross 

 walls. 



Cultures of this alga remain green in the dark for 2 months on 

 Detmer ^ agar plus 2 percent dextrose, as reported by Meier ( 1934 a) . 

 The best growing conditions for this alga in an artificial environment 

 were found by Meier (1934 b) to be in Detmer ^ solution in inter- 

 mittent light when the cultures were kept agitated to favor more 

 equal distribution of the cells, multiplication, and a more uniform 

 lighting condition. It was also found that rubber stopi>ers serve as 

 well as cotton plugs in 300 cc flasks containing 100 cc of inoculated 

 solution for an experimental period of a month. Multiplication of 

 this alga is proportional to the intensity of illumination, ranging from 

 3.76 to 34.1 microwatts/mnr. A higher intensity such as 102.0 micro- 

 watts/mm ' checks the growth. 



