72 THE BOTANICAL MAGAZINE. tVo i. xxi.no. us. 



(A' Lunularia, farther only with one potassium salt, the 

 chloride 



When one of us made his first studies in this line (1892) 

 the behavior of magnesium salts to potassium salts and sodium 

 salts was of eourse compared with that to calcium salts. No 

 toxic action of potassium salts had been observed however, 

 while a retarding action of potassium salts was observed in 

 one case and an accelerating action in another, on the toxic 

 action of magnesium salts. The experiment was the following. 

 In a 0.2 per mile solution of magnesium sulphate Spirogyra 

 communis died in 5—7 days, while upon addition of 0.1 per 

 mile dipotassium phosphate in 15—18 days and on the other 

 hand upon addition of 0.1 p.m. monopotassium phosphate in 

 3 days. In a solution of 0.2°/o monopotassium phosphate 

 and even on further addition of 0.2 °/ KN0 3 the alga can 

 remain alive for a series of weeks. 2) But already at a concen- 

 tration of 1 ^ and a temperature of 12-20° various salts are 

 injurious which are harmless at 0.2-0.5 per cent. At 4— 6°C the 

 resistance power is greater, especially with the larger kinds. 

 Further a gradual adaptation may be reached. Spirogyra cells 

 that had been kept in 0.5% NaCl solution can resist a 1% 

 solution longer than otherwise. 



Effects of physiologically not balanced culture solutions on 

 algae (Spirogyra) w r ere observed years ago by one of us. Thus 

 it was noticed that a considerable preponderance of lime over 

 magnesia retarded the cell division; an undue preponderance of 

 phosphoric acid and nitrogen over potassa rendered starch 



') Cf. V. Ostekhaut, vol. II. No. 11 of the Publications of the University of 

 California, 1906.— 



2 ) The salts applied should be chemically pure. Often a very faint trace of 

 popper is present, when the salts had been recrystallised from common distilled water. 

 Only water distilled from glass vessels should serve for recrystallisation. In such 

 distilled water Spirogyra can remain alive for a very long time. The flasks for the 

 tests with Spirogyra should be first washed with hydrochloric acid, then with this 

 distilled water. The amount of solution applied should not be too small. Generally 

 lOd CC. Berved for a small number of filaments, because otherwise some dying filaments 

 losing nutrient compounds by exosmosis can thus influence the resistance power of the 

 neighboring filaments. 



