to the Plant Cell. 
5°9 
It would seem that this power of calcium is that of a specific antidote 
for magnesium, just as specific antidoting properties have been demonstrated 
between various other elements. 
The antidoting power of calcium was demonstrated by Kearney and 
Cameron (’02). In an extensive series of experiments they found that 
calcium nearly always had marked ability to decrease the toxicity of both 
magnesium and sodium salts for seedlings of Lupinus albus. Kronig and 
Paul (’97) have shown that a similar marked decrease of toxicity for bacteria 
was obtained when the chloride of sodium, potassium, magnesium, zinc, or 
cadmium was added to a solution of mercuric bichloride. Clark (’01) 
demonstrated that the toxic value of mercuric bichloride for fungi was 
greatly diminished by the addition of sodium chloride or hydrochloric acid. 
Pigorini (’07) has even been able to show that such a poisonous substance 
as sodium thiosulphate was able to diminish the toxicity of silver nitrate 
solution for Carassius auratus. True and Gies (’03) have shown that the 
toxicity of salts of the heavy metals to seedlings is greatly reduced by the 
addition of salts of sodium, magnesium or calcium. Loeb (’06) has found 
that the effect of magnesium in producing rhythmical motions in a jelly-fish 
may be inhibited by the addition of an equivalent amount of calcium or 
potassium to the water. Osterhout (’06) has reported that pure sodium 
chloride solutions are quite toxic to certain marine plants. The toxicity is 
much diminished if calcium chloride be added, and is still further diminished 
if both calcium and potassium chlorides be added to the sodium chloride 
solution. 
While it is no doubt true that a very large number of plants require 
that some sort of a ratio between calcium and magnesium be maintained, 
it is difficult to fit the theory of the necessary calcium-proteid compound 
to a vast number of plants, which normally live with little or no calcium. 
It seems more plausible to postulate (and at present it appears impossible 
to do more) that calcium salts are able to perform some specific antidoting 
powers against magnesium in the plant. There appear to be instances 
where the antidoting may be performed by sodium, or by potassium as well 
as by calcium. Future investigation will have to determine the nature of 
this antidoting power. 
Mayer (’69), Raulin (’69), and Winogradsky (’84) demonstrated that 
yeast and certain other fungi could grow in the absence of calcium, but 
required magnesium. Molisch (’95) showed that the same requirements 
held for Microthamnion , Stichococcus and some other Algae. Sestini (’91) 
showed that the functions of magnesium could only be imperfectly performed 
make any particular difference to these or any other plants unless, indeed, it be proved 
that phosphoric acid is relatively abundant. On the other hand it is possible that the com- 
paratively large amount of sodium present in the sea water might act as a partial antidote for 
magnesium. 
