NO. 6 EFFECTS OF LIGHT ON ALGAE MEIER 3 



best in the blue and violet. 5220 to 4260 A ; less favorable in the red 



and a small part of the orange, to 6130 A; and poorest in the 



green, 5680 to 5240 A. Chlorophyll was present in all the regions 

 of the spectrum studied separately. 



Thirty years later Teodoresco (1929) reports about 170 experi- 

 ments in which he investigated two main regions of the visible spec- 

 trum, using both colored solutions and glass filters. He measured 

 the energy transmitted through both sets of filters by means of a 

 thermopile and a galvanometer and equalized the intensities. In mea- 

 suring the light intensity he used a screen of water and copper acetate 

 to eliminate the effect of the infrared radiation. Using a variety of 

 hepatics, vascular cryptogams, and phanerogams, Teodoresco found 

 that in the red-orange, 7750 to 6440 A, the general configuration of the 

 l)lant was abnormal, while in the blue, 5090 to 3660 A, the general ap- 

 pearance of the plant was normal and similar to plants grown in the 

 shade or in white light. Fern germination was retarded in the blue 

 light. 



Nadson (1910) grew SticJiococciis hacillaris Naegeli under bell 

 jars of colored solutions and found that red-yellow light caused ab- 

 normally shaped cells and disorganized chromatophores of a pale 

 yellow-green color. Cultures, 3 to 6 months old, grown in blue light 

 finally attained a stage of development similar to the cultures in white 

 light which were more normal in color and morphology. 



Otto Thelen (1910), growing oats, beans, and other plants under 

 light filters, obtained maximum production in the bright yellow and 

 yellow-red light ; the bright red light gave more than a third less dry 

 weight, the blue still less, and the red and dark red, the least. The 

 plants grown in white light produced almost as much dry weight as 

 those grown under the yellow-red filter. 



Dangeard (1912) immersed a piece of white blotting paper into a 

 culture flask of ChloreUa vulgaris growing in Knop solution, stretched 

 it on the wall of a culture dish, and radiated it in a quartz spectrograph. 

 The maximum action of the rays as indicated by the differences of 

 vegetation was in the chlorophyll absorption bands. The algae grew 

 best in the region 6700 to 6600 A, less in regions 6800 to 6700 A 

 and 6600 to 6300 A, with a feebler growth in 6300 to 6000 A, and a 

 very feeble growth in the range 6000 to 5700 A. No trace of the 

 alga was visible from 5200 to 4000 A. 



Klebs (1916-1917) showed that very striking formative changes 

 can be induced in prothallia placed in dift'erent regions of the visible 

 spectrum. He indicated that intensity and duration of light as well 



