376 BOTANICAL GAZETTE [OCTOBER 
in such a way that the aluminum disk floated at the surface of the 
solution. Each disk was floated on about 3 liters of solution in an 
agate enameled pan. The seeds were germinated in a solution of 
the same composition as that designed for the experiment. None 
but sprouted seeds were used. Each disk originally held about 
rooo seedlings, but careful selection brought the number down to 
about 200. 
In attempting to study the effect of a small amount of calcium, 
special precautions are necessary, owing to the abundance of cal- 
cium compounds in our environment. The seeds and apparatus 
used must be washed in dilute HC] and rinsed with distilled water 
of undoubted purity. The cultures must be carefully protected 
from dust, especially dust from plastered walls, or from cement 
floors, which might carry salts of calcium, since 1 part per million 
of calcium may produce distinct effects. It is necessary to work 
in somewhat the same way as one works with cultures of bacteria. 
The antagonism of calcium and sodium has been a matter of 
record in connection with OsterHouT’s data. The case is illus- 
trated by the cultures shown in fig. 1, which show the toxic action 
of 4000 p.p.m. NaC] and the antidoting action of CaSO,, CaO, and 
Mg(HCO,),. The wheat seedlings shown in the figure were similar 
at the outset and grew 7 days in the respective cultures. The 
concentration of 4000 p.p.m. NaCl is about the toxic limit for 
wheat seedlings under these conditions, yet 30 p.p.m. of a calcium 
salt antagonized completely the toxicity. Magnesium bicarbonate 
was not so successful in overcoming the bad effects of sodium 
chloride. 
A further illustration of the antagonistic action of calcium is 
shown in table I, which gives data pertaining to wheat plants 
grown in solutions of sodium chloride with and without the addition 
of CaO. It will be seen that (1) measured by ash content and by 
dry weight of plants the addition of 30 p.p.m. CaO was beneficial 
to growth; (2) the amount of NaCl absorbed by the plants was 
not decreased when CaO was added. In the case of cultures 4 
and 5 of table I the ratio of NaCl to total ash is 1:1.9 where only 
NaCl was present in the solution and 1:2.3 where both NaCl and 
CaO were present. From this it would seem that the calcium salt 
