Ig09] LIPMAN—EFFECTS OF SALTS ON BACILLUS 123 
Discussion 
Briefly reviewing the results with B. subtilis above given, we note 
their significance from the scientific as well as the practical stand- 
point. Of the four chlorids tested singly, NaC] is the only one stimu- 
lating ammonification at the concentrations employed. It is not 
unlikely, however, that KCl has a similar effect at a slightly lower 
concentration. 
CaCl, is the most toxic of the chlorids used. In this feature, B. 
subtilis appears to resemble animals, for which calcium is very toxic, 
and not plants; since for plants, with which bacteria are now classed, 
calcium is the least toxic of the four chlorids. This fact may have a 
bearing on the future classification of bacteria. 
The strong antagonism exhibited in some of the combinations of | 
salts employed speaks eloquently for the fact that balanced solutions 
are as necessary for the optimal development of bacteria and allied 
forms as for the higher plants and animals, a fact which has been 
denied in a recent publication of LoEw and Aso (13). This is of the 
greatest practical significance when applied to soil bacteria, and 
especially those of alkali soils, in which, owing to the excessive amount 
of one or more salts, the bacterial activity is inhibited, and conse 
quently plant food is not made available to the higher plants. 
Because the salts experimented with are all found in our soils’ in 
larger or smaller amounts, and in some soils are present in excess, 
it is a matter of practical importance to apply the results of researches 
on the physiology of plants and bacteria to improve such alkali 
lands. There is no doubt in my mind that when we have. learned 
to coordinate the results of researches on plants and soil bacteria, and 
_ to apply them in the field, we shall have at our command a method 
E for the control and profitable cultivation of alkali lauds, of which so 
_ Many thousands of acres are merely vast wastes at the present time. 
Lastly, the results of these experiments are significant because 
they open up an unexplored field of bacterial physiology, in which 
further researches will teach us much. 
4 Summary aes 
____ 1. Each of the four chlorids (CaCl,, MgCl,, KCI, NaCl) is toxic 
: for B. subtilis, in the order given, the first being the most toxic and 
