MAGNESIUM SALTS. 57 



capable of migrating in plants than is the calcium phosphate, at least 

 in neutral media and in the cytoplasm and its intercellular connections. 



The alga Spirogyra is especially well adapted to show the influence 

 of magnesium salts upon the production of portein matter. This influ- 

 ence may be twofold, (1) in facilitating the assimilation of sulphur and 

 nitrogen from sulphates and nitrates the albumin formation as such is 

 increased, and (2) in making the assimilation of phosphoric acid possi- 

 ble, nucleoproteids may be formed, so that division of the nucleus and 

 growth can proceed. If growth is as energetic as the formation of pro- 

 tein no accumulation of protein will take place, all being organized for 

 the wants of the multiplying cells. However, by reducing the amount 

 of phosphate to a trace multiplication can be very much retarded or 

 stopped altogether, while albumin formation may go on; hence in this 

 case an accumulation of albumin takes place either in the cell sap or 

 in the cytoplasm or in both. 



These conclusions can be very easily verified by studies with Spiro- 

 gyra, for which the bicarbonate, obtained by dissolving magnesium 

 carbonate in water charged with carbonic acid, is a very favorable form 

 of magnesium. Thus a most energetic growth was observed with the 

 following- composition : 



Per rnille. 



Magnesium bicarbonate 0. 5 



Magnesium sulphate 1 



Calcium nitrate 5 



Monopotassium phosphate 05 



Potassium nitrate 2 



Ferrous sulphate Trace. 



The supposition that the favorable action of the magnesium bicar- 

 bonate consists simply in a " neutralization of acids" formed in the 

 process of metabolism, can not be correct, since calcium bicarbonate by 

 no means shows the same beneficial influence, and besides in the latter 

 case the above culture solution would contain such an excess of lime 

 over magnesia that the assimilation of phosphoric acid might be 

 retarded, involving a slower development. 



The foregoing makes it intelligible why in the absence of magnesium 

 salts the multiplication of cells is stopped, the nucleus not being able 

 to increase to the point where division sets in. In the mixture of dif- 

 ferent salts occurring in plants there is sufficient opportunity for mag- 

 nesia to combine with phosphoric acid, and the secondary magnesium 

 phosphate thus formed can, in passing into the tertiary salt, yield some 

 free phosphoric acid. The tertiary salt remaining can easily be redis- 

 solved b} 7 weak organic acids, and thus yield again the secondar} 7 

 phosphate, which ma}^ in turn be utilized for the assimilation of phos- 

 phoric acid. Rapidly growing parts general^ develop an acid reaction 

 in the cell sap, which is of advantage. 



The rapidly proceeding" cell division requires the most favorable 

 conditions for the assimilation of phosphoric acid. 



