240 .) Report oN Crop PRODUCTION OF THB 
“1. That sodium is never totally absent from plants; and that 
“2. If indispensable, but a minute amount of it is requisite. 
“3. That the foliage and succulent portions of the plant may 
include a considerable amount of sodium that is not necessary 
to the plant; that is, in other words, accidental.” 
Concerning the replacement of potassium by sodium the same 
author concludes ‘that the sodium which appears to replace 
potassium is accidental, and that the replaced potassium is acci- 
dental also, or in excess above what is really needed by the 
plant,” and leaves us to infer that the quantity of these bodies 
absorbed depends to some extent on the composition of the soil, 
and is to the same degree independent of the wants of vegeta- 
tion. 
EXPERIMENTS AT THIS STATION. 
These experiments were begun in the winter of 1898-1899 and 
were continued in the winter of 1899-1900. They were carried 
on in a forcing house devoted entirely to plant nutrition and 
were in theeimmediate charge of Mr. O. M. Taylor, who gave the 
plants the most painstaking care under conditions such as to 
insure the experiments against errors and accidents, 
THE PLAN AND DQBTAILS OF THE EXPERIMENTS. 
The soil—Plant feeding experiments with natural soil are in ~ 
some respects very unsatisfactory. With such a medium for 
growth, even the most sterile that can be found, it is not pos- 
sible to control the supply of plant food within desirable limits. 
On the other hand no perfectly sterile artificial soil has been 
discovered which presents conditions the most favorable for 
plant growth. 
In these experiments pure quartz sand has been used. This 
was ground from quartz rock by the Berkshire Glass Sand Co., 
Cheshire, Mass. The degree of fineness admitted of the sand 
nearly all passing through a sieve .025 inch in mesh. ‘Tests of 
this sand for phosphoric acid and potash gave no trace of the 
former and an average of only .00078 per ct. of the latter. 
