Study of Spirogyra nit id a. 231 



579 [L\x. There is here an overlapping of 4 pp., but this is 

 too small a band to make any appreciable difference in the 

 physiological results. In the bine and violet, likewise, the 

 bands overlap somewhat. The bine extends from 4/6 W- 

 to 435 pp., while the violet is from 449 pp. to 417 pp., a 



lap of 14 pp. 



After the foregoing work had been completed it was 

 found that Landolt* had constructed what he terms a 

 "color filter," for which he makes use of inorganic 

 solutions almost exclusively, and uses not less than two 

 layers for each colored band. For the yellow which 

 extends from 614 pp. to 574 PP- he nnds three la Y ers are 

 necessary, viz.: 1. Nickel sulphate; 2. Potassium bichro- 

 mate; 3. Potassium permanganate. Landolt does not give 

 an orange band distinct from red and yellow. He fills 

 tightly stoppered, fiat, glass bottles with these solutions, 

 standing them closely against one another in metal frames. 

 While this form of apparatus might be constructed on such 

 a scale that it would be available for biological work, it is 

 believed that the simpler scheme above given is moie read- 

 ily adapted to the conditions required for such investiga- 

 tions. The glass dishes and earthenware bowls may be 

 obtained in so many sizes, that large or small objects can be 

 accommodated with equal facility. 



Experimental Study of Spirogyra nitida. 



Conditions having been obtained, under which the plant 

 could be grown for a long period in light composed of but 

 a small number of wave-lengths, the effect of these narrow 

 bands upon the growth and composition of the individual 

 cells remained to be determined. 



To this end Spirogyra nitida was placed in the culture 

 bowls and its development watched. The most favorable 

 conditions for the growth of the plant were found to pre- 

 vail when a layer of clean, washed sand covered the bottom 

 of the bowl, having planted in it about six actively grow- 



* Sitzungsber. d. Kgl. Akad. d. Wissensckaftenzu Berlin, (1894) Vol. 38. 



