1897 | RELATION OF NUTRIENT SALTS TO TURGOR 4Ul 
that they have been reserved for discussion until after all of the 
tables have been presented. 
1. Potassium presented in solution to the roots of plants 
causes the cells of both root and stem to exhibit a higher turgor 
than they can do when it is replaced by sodium. There is no 
conceivable reason’ for suspecting the Na of depressing the 
turgor; in fact the ‘‘normal”’ solution in some experiments con- 
tained Na, and in others did not, without any difference appear- 
ing in the results. So we may state it, that potassium ts a factor, 
direct or indirect, zx the turgor of the plant. 
2. There is no experimental ground for attaching this significance 
fo any other constituent of the mineral food.” 
It need hardly be stated here that, in common with any 
molecule of any kind dissolved in the cell sap, the elements if 
present in solution must contribute to the turgor. Nor is it 
impossible that they are sometimes important factors in it; but 
if they are, our methods cannot demonstrate it. In some 
instances, as when plants in an incomplete solution are able for a 
time to grow normally and to maintain at least a normal degree 
of turgor, we can say decidedly that their presence does not 
contribute to the turgor. Fagopyrum and Zea grown without 
Ca, and Zea without HPO, illustrate the case against these two 
food elements. Again, when in the absence of some food con- 
Stituent the depressed growth was able to produce a very high 
turgor, it is improbable that the substance in question is ever a 
considerable part of the plant’s osmotically active matter. 
HPO,, Mg, and SO, are such substances, whose absence 
‘Was accompanied by fa growth and high turgor. When the 
_ absence of K, on the other hand, stunted the growth (compare 
t and 3 of Zea ) the turgor still remained low. 
The behavior of the various plants grown in distilled water 
is worthy of more than the passing notice it can here receive. 
_ Many plants will grow very rapidly in pure water until their 
Stored-up food is exhausted. In consequence at once of the 
‘Tapid growth and of the want of nourishment they have a low tur- 
3 : eames iS prods of settnitation: might pee oat to this list. 
