MAGNESIUM SALTS. 51 



phenomena closely resembling those produced by potassium oxalate; 

 but while in a 1 per cent solution of magnesium sulphate the nucleus 

 will swell up after twelve hours, in a 0.5 per cent solution of potas- 

 sium oxalate it will do so in a much shorter time. 



The noxious action of magnesium salts also soon becomes evident 

 in the roots of seedlings. Thus Vicia and Pisum do not start lateral 

 roots when kept in a solution of 0.5 per cent magnesium sulphate or 

 nitrate, and the root cap and epidermal cells die after a few days. In 

 a solution of calcium nitrate of equal strength, however, development 

 continues. Seedlings of Phaseolus placed in a solution of 0.1 percent 

 magnesium sulphate with 0.1 per cent monopotassium phosphate 

 showed injury to the roots after five days, and the entire plant suc- 

 cumbed soon afterwards. Similar observations had been made by 

 Wolff, by Raumer and Kellerman, and by others, but all failed to 

 recognize the true cause and to ascertain that lime salts alone act as 

 the specific remedy. 



Raumer" observed that in Phaseohis multiflorus kept in various cul- 

 ture solutions there was a detrimental effect much sooner when lime 

 alone was absent than when both lime and magnesia were absent. 

 The difference was most striking in the main roots and also in the 

 number and vigor of the lateral roots. Here, then, the noxious effect 

 of magnesia in the absence of lime is again manifested. 



The writer has made a special study of the development of roots in 

 culture solutions free from lime and from magnesia, using branches of 

 Tradescantia for this purpose. These have calcium as well as magne- 

 sium salts stored up in their nodes, and hence some development of 

 roots is possible even in distilled water. Nevertheless, a most striking- 

 difference was noticed, the roots in the culture solutions containing 

 lime, but not magnesia, producing a "dense forest" of root hairs that 

 reached a length of one-fourth centimeter, while the roots in solutions 

 containing magnesia but no lime, although larger than the others/' pro- 

 duced only a few short hairs. The lack of lime in these roots was felt 

 especially in the epidermis, the interior parts being able to draw a 

 sufficient amount of lime from the stem. Indeed, a microchemical test 

 showed the presence of lime in the ash of these roots, gypsum needles 

 forming when treated with a little sulphuric acid. 



aLandw. Vers. Stat., 1883, Vol. XXIX, pp. 254 and 268. 



''These roots were 4.1 cm. long, while those in culture solutions without magnesia 



were only 3.2 cm. long. The composition of the complete culture solution in the 



above case was as follows: 



Per milk-. 



Monopotassium phosphate 0. 1 



Potassium nitrate 5 



Sodium sulphate 2 



Calcium nitrate 5 



Magnesium sulphate 2 



Ferrous sulphate Trace. 



