1913] LIPMAN & WILSON—TOXIC SALTS AND ACIDS 417 
It is clear from the data given in table III that both wheat and 
vetch are stimulated by the presence in the soil of MnSO, until the 
concentration of the latter there reaches an equivalent of 2000 ppm. 
for the wheat, and 800 ppm. for the vetch. Indeed, the total 
yields of dry matter obtained from the wheat growing in the pots 
with the highest concentrations of MnSO, surpass quite markedly 
the yields obtained in any of the pots of the other series described 
in this paper, and which were planted contemporaneously with the 
former. In the case of the vetch, the stimulation does not seem to 
be as great as in the case of the wheat, but from one series of experi- 
ments it is difficult to say if stimulation actually stops for the 
vetch at a concentration of 2000 ppm. of MnSO,, since the poor 
growth obtained there may have been due to experimental error. 
These results are an interesting contribution to the subject of 
the effects of manganese salts on plants. It is not our intention 
here to discuss the large number of investigations bearing on this 
subject, especially since this has already been so well done by 
LLEY, in the work above referred to. In general, however, 
it would appear from such a review that the largest number of 
investigations on the subject indicate a stimulating power of man- 
ganese sulphate for plants, results with which ours are in accord. 
There are several cases, however, in which manganese compounds 
have been observed to depress crop yields, and this point would 
seem particularly to deserve brief discussion. The experiments 
dealing with this subject which have thus far been carried out have 
included tests of many different manganese compounds, and a com- 
parison of the results obtained with different compounds in trying 
to determine the specific effects of manganese would seem to us to 
be manifestly unfair. One of us has pointed out elsewhere? that 
the anion as well as the kation of salts must be taken into considera- 
tion when the effects of salts on living organisms are studied. 
such be the case, and we have every reason to believe that it is, 
then only the experiments bearing on the effects of MnSO, on plants 
should be compared when that subject is studied, and not the effects 
of the nitrate, chloride, oxide, sulphate, and other compounds. 
When that is done, it will be found that the percentage of investi- 
9 Centr. Bakt. 33:305. 
