41 



calcium in the form of calcium uitrate and others with solutions in which 

 the calcium nitrate was replaced by equivalent quantities of strontium 

 nitrate and of barium nitrate. Only the plants in the normal solutions 

 showed a strong and vigorous development, while those in the barium 

 and strontium solutions exhibited gradually an injurious action, and 

 when at the time of their earlj^ death the experiment was terminated, 

 the following data were obtained: 



Action of calcium, strontium, and harimn salts. 

 BUCKWHEAT SHOOTS. 





Nitrate of 

 calcium. 



Mtrate of 

 strontium. 



Nitrate of 

 barium. 



Average weight of one stem . .. 



b. 352 



0.260 

 .080 



0.187 



Average weight of one leaf 



.198 



.050 



BARLEY SHOOTS. 



Average weight of one plant. 

 Ratio of dry weight 



1.50 

 100. 00 



0.67 

 44.06 



0.51 

 34.00 



It will be noticed that the action of the barium solution was more inju- 

 rious than that of the strontium solution. Branches of the other three 

 Phanerogams mentioned were used, here those in the barium and stron- 

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

 containing calcium nitrate remained healthy and developed new leaves. 

 Control cases in distilled water showed here also that the injury in the 

 case of the barium solution 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 ac'tions are retarded by the 

 addition of lime salts. 



Now, if calcium salts act only in processes of metabolism it might be 

 inferred that such processes could be performed as well by strontium 

 salts, the main properties of the salts of both elements being to a cer- 

 tain degree alike. Thus, strontium oxalate dissolves with difficulty 

 in water (1:12,000), as does also the sulphate. The latter, however, 

 being less soluble (1 : 6,895) than calcium sulphate (1 : 488), it might be 

 supposed that the assimilation of sulphur is seriously lessened. How- 

 ever, considering the diluted state in which the phosphates enter and 

 still how well they are assimilated, 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 pro- 

 cesses of metabolism in plants have to be assumed for calcium salts 

 which it would be impossibre for strontium salts to perform.^ Thus 



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

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

 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 Diatoms, 

 FlagelJata, or Infusoria in presence of sufficient lime. 



