43 



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

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

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

 antidote for magnesium salts. ' Nothing- can replace them successfully 

 in this case, not even nourishment with organic matter.* Microscopi- 

 cal examinations of Spiro(fyra cells exposed to the exclusive action of 

 maunesiiim salts show that the nucleus is attacked first and then the 

 chlorophyll body is injured, the ])henomena 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 potassium 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 \lcia 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 per cent 

 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 

 Wolf, by Kaumer and Kellerman, and by others, bnt all failed to 

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

 the specific remedy. 



Raumer^ observed that in Phaseolus multifforvs 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 i)urpose. These have calcium as well as magne- 

 sium salts stored up in their nodes, and hence some develo])ment 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 



1 These observatious the writer desrribefl in Flora, 1892, and also in Landw. Vers. 

 Stat, of the same year. 



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



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

 prevent it, as do calcium salts. 



* It may be mentioned that Spirogyra remains alive for fi-om five to six weeks if 

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

 tion and respiration soon reach a suitable eqiiilibrium. 



" Landw. Vers., 1883, Vol. XXIX, pp. 254 and 268. 



