82 THE BOTANICAL MAGAZINE. CV oi. xxi. No. 21a. 



It will be scon that the increase of the potassa in the form 

 oi sulphate exerted some counteraction on the depression by 

 an excess of magnesia but only lime was able to counteract 

 fully that injurious effect. 



A similar experiment was made with spinach. After one 

 month the young plants had reached only 2cm. in height at 

 the excess of magnesia and at this excess + an extradose of 5g. 

 KC1 per pot, the average height was quite the same, while at 

 the addition of calcium carbonate, the average height was 

 4.6 cm. 



SUMMARY. 



1. The view recently expressed that "physiologically bal- 

 anced solutions have not been made use of by botanists," can 

 hardly be sustained, since Knop's culture solution must be 

 regarded as such a solution. Lower forms of algae and fungi 

 do not require physiologically balanced solutions. 



2. Potassium sulphate and nitrate are only injurious for 

 plants when the concentration is abnormally high. Potassium 

 chlorid at 0.3^ exerts after several weeks a slow injurious 

 effect on Spirogyra, but on Phenogams not for many weeks, 

 even at 0.5^. 



The final death of Spirogyra cells in dilute solutions of 

 potassium sulphate or nitrate is merely due to the one sided 

 nutrition and exhaustion. — 



3. Potassium salts can retard but not prevent the toxic 

 effects of magnesium salts. The cause of this retardation is 

 entirely different from the prevention of this toxic action by 

 calcium salts. 



4-. Some interesting observations may be made on Spiro- 

 gyra. kept in imperfect culture solutions. Thus, e.g., in a 

 solution containing only KC1 and MgCl 2 the cytoplasm can 

 remain long alive after the nucleus is killed, recalling Gerassi- 

 mow's cells without a nucleus; in a solution containing only 

 K 2 S0 4 and CaS0 4 abundance of rhizoids is formed. This 

 rhizoid formation depended in our eases only upon the salts in 

 solution, while in other eases it depends upon the contact with 



