26o 
Walter Stiles and Ingvar Jorgensen. 
Again, Osterhout found a very well marked antagonism between 
potassium and sodium. Here, again, Osterhout worked with higher 
concentrations. 
Hansteen criticises this result of Osterhout’s in that it may 
have been due to his keeping the seeds in the solution. The seeds 
are supposed to have excreted substances which eliminated the 
toxic effect. This criticism seems, however, to be scarcely valid, 
as one would expect the excreted substance to paralyse the effect 
in all the solutions used by Osterhout. 
Osterhout is further criticised in that he says antagonism does 
not enter into dilute solutions, while Hansteen shows there is an 
antagonism even in solutions of as low a concentration as 
But Hansteen’s whole work is open to the very serious criticism 
that it is based on observations of the appearance, and measure¬ 
ments of the dry weights, of roots of water cultures grown in 
duplicate. Anyone who has conducted research work involving the 
use of water cultures will realise how unsafe it is to generalise on 
such cultures done only in duplicate owing to the great variability 
of such plants even when growing under exactly similar conditions. 
So that while it seems safe to accept Hansteen’s general result of 
the antagonism between the nitrates he used, yet it would appear 
more satisfactory to delay the acceptance of the actual optimum 
ratios he records until they have been confirmed by a more numerous 
series of controls or by some other method. 
In order to arrive at the reason for the depoisoning effect of 
calcium on magnesium or potassium, Hansteen performed some 
experiments in “ double cultures.” In these, seedlings of Wheat or 
Oat were grown with some side roots in a tube containing a pure 
magnesium or potassium nitrate solution and with other side roots 
of the same seedling in a pure calcium nitrate solution or a 
mixture of calcium nitrate with magnesium or potassium nitrate. 
In all such cultures the roots growing in the tube containing calcium 
nitrate were healthy while those in pure potassium or magnesium 
nitrate perished. The same result was obtained when the plumule 
was in gypsum. In all such experiments it was shewn by micro¬ 
chemical examination that plenty of calcium had diffused into those 
roots immersed in magnesium or potassium nitrate. From this 
result Hansteen concludes that the antagonism between calcium 
and magnesium or potassium is a surface effect, and not due to 
chemical action inside the cell. 
