iq 1 7l CHIEN—SPIROGYRA 409 





Some experiments were made with the smaller kind of Spirogyra 

 in order to see whether antagonism occurs. BaCl 2 and SrCl 2 have 

 no antagonistic action on each other. CaCl 2 and CeCl 3 (neither of 

 which causes contraction of the chromatophores by itself) are able 

 to antagonize BaCl 2 , and CeCl 3 is more effective than BaCl 2 . 

 The chromatophores do not contract when placed in a mixture 

 made by adding 10 cc. of 0.04 M CeCl 3 to 90 cc. of 0.08 M BaCl 2 

 in an hour and a half (after which the experiment was discontinued) ; 

 while if 10 cc. distilled water is added to 90 cc. of the same BaCl 2 , 

 contraction begins after 1.5 minutes. Antagonism is obtained 

 also by mixing 60 cc. of o. 1 M Cacl 2 with 40 cc. of o. 1 M BaCl 2 . 

 In this mixture no contraction occurs in 1 hour, while if 60 cc. of 

 distilled water is used in the mixture in place of CaCl 2 , the con- 

 traction occurs in 2 minutes. The proportions here mentioned are 

 approximately the optimum ones for each mixture. 



Summary 



1. The chloroplasts of certain species of Spirogyra contract 

 away from the cell wall in a peculiar and characteristic fashion in 

 solutions CeCl 3 , BaCl 2 , and SrCl 2 (in the case of the smaller kind 

 in the last 2 only). The effect is observed in dilutions as great as 

 0.00005 M CeCl 3 (in the case of the larger species), and in o. 0001 M 

 BaCl 2 . SrCl 2 also produces this effect, but not at such great dilu- 

 tions as CeCL and BaCl 2 . 



In the smaller species of Sp 



2 is 



inhibited when BaCl 2 is mixed with CeCl 3 or CeCl 2 in proper 

 proportions. 



Laboratory of Plant Physiology 



Harvard Umv 





