254 
Walter Stiles and Ingvar Jorgensen. 
Earlier Work and Work not dealing directly with 
Antagonism. 
The first indications in plant physiology of the existence of 
the phenomena we are considering, were very naturally observed 
with the advent of the method of water-culture, where the con¬ 
stitution of the nutrient solution is under the control of the 
investigator. Sachs (34, 35) in his classical researches with this 
method observed that plants grew best when a certain balance 
was maintained between the various constituents of the nutrient 
solution; a result which becomes in some part explicable now on 
the theory of antagonism. Some years later Boehm (3) showed 
that the toxicity produced by certain salts when present alone in 
solution—an effect which had previously been noted by Wolf (40) 
in the case of weak solutions of potassium, sodium and ammonium 
salts, and of very weak solutions of magnesium salts—could be 
lessened or eliminated by the addition to the solution of small 
quantities of calcium salts, which Wolf had shown were much less 
toxic in pure solution than salts of magnesium or of the alkali 
metals. 
In 1898 Benecke (1) also showed that the toxic action of 
potassium salts was eliminated in the presence of calcium salts. 
One of the results of the water-culture method has been the 
emphasising of Sachs original observation of the necessity for a 
balance between the various constituents of the nutrient solution, 
and special attention has been directed towards the optimum ratio 
of calcium and magnesium in nutrient solutions. Some workers 
at any rate seem to have obtained definite evidence of a calcium- 
magnesium ratio best suitable for plant growth. But the results 
of different workers show little consistency in details, and here it 
will be sufficient to refer to the work of Loew (15), Loew and May 
(19), Kearney and Cameron (12), Gile (9), True and Bartlett (38) 
and Tottingham (37), who have all produced evidence of the balance 
required between different nutritive substances, and in particular 
between calcium and magnesium, for the production of an optimum 
absorption of salts, or growth. 
Before ideas on antagonism had taken a definite form Loew 
(15, 16) elaborated a theory to account for the toxic properties of 
magnesium when calcium was not present in sufficient quantity. 
He supposed calcium is a necessary constituent of the chlorophyll- 
bodies and nucleus, and when magnesium is present in great excess 
this takes the place in those bodies that should be occupied by 
