f '05 ) 



trated solutions must necessarily become harmful if' it were only on 

 account of their strong osmotic action on plant-cells ; in other words, 

 it is possible to determine the toxic limit of plasmoljsing substances. 

 In these cases the results of weighing are different in that the tissues 

 in the salt-solution obviously lose weight but recover weight again 

 when placed in water, if thej have remained undamaged. If during 

 the c/(^plasmoljsis death might occur, this can afterwards be recognised 

 by a diminution of weight. 



By this method I have been able to ascertain that the potato- 

 tuber is rather sensitive for plasmoljsing agents. Pieces of this organ 

 appear to be damaged when thej have stayed for 24 hours in 

 0.4 gram mol. NaCl (2.347o), J^i^d are then placed in water. We 

 ^vill not decide whether death took place already in the salt-solution 

 or on entering the water ; sometimes, however, the grey discoloration 

 already began to appear in the solution. A solution of 0.3 grammol. 

 NaCl (1.757o) is perfectly harmless when acting for a day. Now 

 other parts of plants offer a much greater resistance to neutral salts. 

 The limiting concentration of NaCl for pieces of beetroot, e. g., lies, 

 when acting for a day, at between 1 and 1.5 grammol.; I did not 

 determine this limit more accurately. Similar values are furnished 

 by various other parts of plants, such as the tuber of Colchicum 

 autumnale, the leaf of Aloe dichotoma and Aloe succotr'ma. 



For KBr, KNO3, the molecular concentration at which pieces of 

 potato begin to be injured is pretty much the same as that given 

 above for NaCl. For the present, however, it was not my intention 

 to extend this investigation to a greater number of salts, although 

 this would undoubtedly lead to many interesting results, also perhaps 

 concerning the action of ions on the living cell. It only must be 

 mentioned here that with glucose and saccharose, injurious effects 

 on ])ieces of potato began to be noticeable at a concentration of 

 0.5 or 0.6 grammol. which is only slightly higher than with NaCl. 



Interesting observations on the action of salt-solutions on plant- 

 cells have been formerly made by J. C. Costerus ^) ; although they 

 have not been repeated by the weighing-method, I must not omit 

 drawing attention to them, since they seem to point to a different 

 behaviour of the cells in the salt-solution, depending on the presence 

 or absence of oxygen, which may be of importance with regard to 

 what follows. 



The determination of the lowest limit of concentration for which 

 substances are poisonous, led us to investigate whether this limit can 



1) Arch. Nêerland. t. 15. 1880. 



