226 



GILBERT MORGAN SMITH 



ing of the nuclei, which gradually spread until the whole proto- 

 plast was colored black. There was more plasmolysis caused bj' 

 the mercuric chlorid mixtures than by those containing chromic 

 acid. 



Formalin mixtures with the addition of copper salts behaved 

 fairly well as far as the preservation of the green color was con- 

 cerned. There was little difference in the color obtained, the for- 

 malin-copper sulphate mixtures giving somewhat paler shades 

 than the others. In all cases the addition of the copper salt 

 caused a much brighter color than was present in algae preserved 

 in formalin alone. The addition of the copper salt increased the 

 pla.smolytic action of the mixture in the cases of Vaucheria and 

 Spirogyra. As formalin is an unstable compound and also vola- 

 tile, its use as a preservative is not to be recommended, since in 

 e\'ery case one of the more stable mixtures gave equally good 

 results. 



Morehouse's mixture usually preserved the color well, but it 

 caused greater plasmolysis than any of the other mixtures used. 

 When the solution was diluted to a concentration at which there 

 was no plasmolj^sis, then the color preservation was not so .satis- 

 factory. Another disadvantage in the use of this mixture is that 

 molds are apt to appear on the surface of the liquid. 



Ripart and Petit's mixture caused plasmolysis in half of the 

 forms on which it was tried. In the cases in which there was no 

 plasmolysis, the green color was not retained. 



Nieuwland- West's mixture gave a bright green color in all 

 cases except with the Zj^gnemateae, in which a brownish color 

 appeared in the cytoplasm and the chromatophores disintegrated. 

 It was the only mixture which produced a green color and no 

 plasinolysis in Oedogonium. The mixture does not prevent the 

 growths of molds very well, and for that reason its use is not to be 

 recommended except in cases like that of Oedogonium in which 

 no other mixture will give satisfactory results. 



Amann's copper-lacto-phenol was the most promising mixture 

 tried, since the preservation of the algae was perfect in every case. 

 The u.se of this mixture has the disadvantage that the color is 

 not as bright a green as one might wish, the chromatophore ha^■- 



