256 
Walter Stiles and Ingvar Jorgensen. 
fish is surrounded by the egg membrane, and that they are actually 
due to the two kinds of ions mutually hindering one another’s 
diffusion into the egg. 
The work of Loeb on animals has been continued and developed 
by Osterhout with much ingenuity with regard to plants. In order 
to determine the relative toxicity of the various solutions used he 
has made use of four different methods, which will be described in 
connection with the experiments in which they were used. 
Osterhout’s first experiments (23) were made with marine 
plants and his observations on these were afterwards extended to 
freshwater and land plants. Marine plants he found can be divided 
into two groups : those which are quickly killed when placed in 
distilled water and those which can live a long time in distilled water. 
Plants of the latter group are killed much quicker when placed in 
a pure sodium chloride solution isotonic with sea water than when 
kept in distilled water. The poisonous effect of the sodium chloride 
largely disappears if a little calcium chloride is added. In a mixture 
of lOcc CaCl 2 ^ + lOOOcc NaCl the plants live nearly as long 
as in distilled water. If some potassium chloride is added to the 
mixture they live longer than in distilled water, while with further 
additions of MgCl 2 and MgS0 4 they live practically as long as in 
sea water. 
Potassium or magnesium chloride added singly inhibit the 
toxicity of sodium chloride a little, but are not nearly so effective 
as calcium chloride. The mixture NaCl + KCI + CaCl 2 is better 
than NaCl + MgCl 2 + CaCl 2 , which is itself superior to the 
mixture NaCl + MgCl 2 + KCI. 
As Osterhout justly observes the effects must be due to the 
metal ions, as practically the same amount of the same anion is 
always present. Moreover the effect cannot be merely a starvation 
phenomenon as distilled water alone is less harmful than sodium 
chloride alone or the mixture of sodium and calcium chlorides. 
Similar results were obtained with the plants which were 
quickly killed in distilled water, except in their behaviour to the 
latter medium. 
In his experiments with terrestrial and fresh water plants (24) 
a variety of genera were used : Vaucheria, Spirogyra and other 
algae, Lunularia (gemmae), Eqnisetum (spores and prothallia) and 
Wheat seedlings among others. A similar result was obtaineu in 
these cases although diluter solutions were used. 
