April, loo:.] LOEW & ASO.—ON PHYSTOL. BALANCED SOLUTIONS. 83 



an object, as Borge and Kny have observed. In saturated 

 gypsum solution the tendency to show geotropism is strong^ 

 preserved and the cells continue to produce an abundance of 

 starch even after the chloroplasts have gradually turned yellow. 

 This starch formation can be considered as proof that neither 

 potassium nor magnesium of the chloroplast had been replaced 

 by calcium. This yellowing is not observed in the solution of 

 0.2% CaCl 2 even after three months. 



5. Interesting effects can be observed with Spirogyra kept 

 in full, but not balanced culture solutions. 



