New YorK AGRICULTURAL EXPERIMENT STATION, 247 
CONCLUSIONS. 
The conclusion that potash stands in a different and much 
more important relation to the physiological needs of plants than 
does soda cannot be evaded, and there is no reason for modifying 
the deductions drawn from the data of the early investigators. 
A discussion of the substitution of soda for potash in plant 
growth may be answered with reference to (1) substitution in 
guantity and (2) substitution in function. 
Substitution of soda for potash, in quantity—There is no ques- 
tion but that in these experiments the dry matter of those plants 
having access to a very limited supply of potash and a free sup- 
ply of soda contained a much larger proportion of soda than 
where potash was present in abundance. The percentages of 
soda where the potash was deficient were from one-half to five 
times greater than where the salts of both alkalies were liberally 
supplied. In this sense potash was substituted for soda. Limit- 
ing the supply of soda did not effect an equal increase of potash, 
although there appeared to be a tendency in some instances to 
substitute potash for soda. 
Substitution of scda for potash, m function.—The most important 
question in this connection is, Did the increase in soda taken 
up by the plants make good the deficiency of potash by promot- 
ing the growth of the plant to the same extent as the potash? 
In other words, Can soda-be substituted for potash in function? 
This question must be answered in the negative so far as these 
experiments throw any light upon it, and the results here pre- 
sented stand in entire accord with the great mass of testimony 
furnished by previous investigations. 
In these experiments the lack of potash was fatal to the vigor- 
ous development of the plants. This is especially shown in the 
results of 1899-1900 where the supply of potash was limited to a 
very small quantity. While the plant appropriated increased 
amounts of soda when the potash was deficient, this seemed to be 
of no avail in making good the lack of potash. On the other 
hand a lack of soda appeared to be no disadvantage whatever, 
when potash was present in a sufficient amount. 
