50 PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



fatal. On the other hand, judging from the laws of the action of 

 masses, it would naturally be inferred that an excess of lime salts 

 would remedy the evil effects by making- the reverse process possible. 

 As a matter of fact, a detrimental action is observed when plants are 

 treated with sulphate or nitrate of magnesium in the absence of cal- 

 cium salts, an effect which is not observed when the same plants are 

 exposed to the exclusive action of calcium, sodium, or potassium sul- 

 phate or nitrate. These phenomena were foreseen by the writer and 

 may be readily explained by his theory, while the holders of other 

 views have not come forward with an explanation. 



The writer observed that Spirogyra died within four to live days in 

 a 1 per mille solution of magnesium sulphate, hut remained alive for 

 a long time in corresponding solutions of sodium, potassium, or cal- 

 cium. In a 1 per cent solution of magnesium nitrate smaller kinds of 

 Spirogyra will die in from six to twelve hours, but will live a long 

 time in corresponding solutions of sodium, potassium, and calcium 

 nitrate. Spirogyra which had been kept for several weeks in a healthy 

 condition in a solution of 0.1 per mille of monopotassium phosphate in 

 absolutely pure distilled water died within three to four days when 

 2 per mille magnesium sulphate was added to this solution; but when 

 dipotassium phosphate instead of the monophosphate was used, death 

 set in much later; that is, after fifteen to eighteen days. 



Some threads of Spirogyra m,ajuscula placed in a solution (1 liter) 

 containing 0.02 per mille each of magnesium nitrate and ammonium 

 sulphate died in from ten to twelve days, while in the control solution, 

 containing calcium nitrate in place of magnesium nitrate, they were 

 still alive after six weeks, although cell division had stopped completely 

 and the cells exhibited an emaciated appearance owing to the absence 

 of other mineral nutrients. In still another case threads of the same 

 alga were placed in a solution of 1 per mille of magnesium nitrate, while 

 in the control case 3 per mille of calcium nitrate was added." In the 

 former case death resulted in five days, 6 while in the latter the cells 

 were still alive after a number of weeks. Lime salts, therefore, are 

 the antidote against the poisonous effects of magnesium salts/' Noth- 

 ing can replace them successfully in this case, not even nourishment 

 with organic matter."' Microscopical examinations of Spirogyra cells 

 exposed to the exclusive action of magnesium salts show that the 

 nucleus is attacked first and then the chlorophyll body is injured, the 



"These observations the writer described in Flora, 1892, and also in Landw. Vers. 

 Stat, of the same year. 



''The time is probably prolonged when lime salts are stored up. 



c An addition of strontium salts may delay death for a short period, but it can not 

 prevent it, as do calcium salts. 



d lt may be mentioned that Spirogyra remains alive for from five to six weeks if 

 kept in distilled water. Of course any further development is stopped, but assimila- 

 tion and respiration soon reach a suitable equilibrium. 



