CALCIUM AND STRONTIUM. 49 



The actioD of the barium solution was more injurious than that of 

 the strontium solution. Branches of the other three phanerogams 

 mentioned were used; here those in the barium and strontium solution 

 died after eight days, while those in the normal solution containing 

 calcium nitrate remained healthy and developed new leaves. Control 

 discs in distilled water showed also that the injury is due not merely 

 to the absence of lime, but directly to a poisonous influence of the 

 barium and strontium salts. Further tests showed that these poisonous 

 actions are retarded by the addition of lime salts. 



Now, if calcium salts perform and sustain processes of metabolism 

 merely it might be inferred that such processes could be performed as 

 well by strontium salts, the main properties of the salts of both ele- 

 ments being to a certain degree alike. Thus, strontium oxalate dis- 

 solves with difficulty in water (1:12,000), as does also the sulphate. 

 The latter, however, being less soluble (1:0,805) than calcium sulphate 

 (1:488), it might be supposed that the assimilation of sulphur is seri- 

 ously lessened. However, considering the diluted state in which the 

 phosphates enter and how well they are assimilated nevertheless, it is 

 clear that the lesser degree of solubility of strontium sulphate would 

 not be a serious obstacle to the assimilation of sulphur. It may, then, 

 well be asked what kinds of processes of metabolism in plants have to be 

 assumed for calcium salts which it would be impossible for strontium 

 salts to perform." Thus far the defenders of the metabolic theory 

 have given no satisfactory explanation. The writer's previously 

 mentioned theory on the function of lime salts, on the other hand, 

 makes it perfectly clear why strontium salts in certain doses become 

 hurtful and even poisonous for all organisms except the lowest forms 

 of alga' and fungi. 



POISONOUS ACTION OF MAGNESIUM SALTS. 



If the writer's view that a calcium -protein compound participates in 

 the organized parts of the nucleus and chlorophyll body is correct, it 

 might be expected that magnesium salts of the stronger acids would 

 exert a noxious action. The lime as the stronger base would in such 

 a case combine with the acid of the magnesium salt, while magnesia 

 would enter into the place which the lime had occupied in the organ- 

 ized structures, the capacity for imbibition would thereby be altered, 

 and a disturbance of the structure would result which would prove 



a Whether a gradual adaptation to strontium salts could ever take place, or, in 

 other words, whether in the course of many generations strontium-protein com- 

 pounds could gradually be utilized like the corresponding calcium compounds, is an 

 entirely different question. However, in this connection only the simpler kinds of 

 organisms might yield satisfactory results. It may be mentioned that 0.1 per cent 

 strontium nitrate added to the culture water does not, even after months, injure 

 diaton'is, Flagellate, or Infusoria in presence of sufficient lime. 



-jr,i>82 — No. 15—03 1 



