to the Plant Cell. 
537 
It has been shown, for example, that potassium is necessary for starch 
formation, and calcium for starch transportation ; yet neither of these 
elements enters into the composition, either of starch, or of the compounds 
which arise as partial products in the formation of starch. Where phos- 
phorus was lacking, there was an abnormal production of cellulose from 
starch, and in some cases erythrodextrin was formed from the starch. 
These effects may very probably have been due to the absence of the 
proper enzyme, which in normal cells converts starches to the various 
sugars. In turn the absence of the phosphorus may have been responsible 
for the non-formation of the requisite enzyme. In such an event, it shows 
that the influence of the element in question is an indirect one. 
The fact that there is reason to believe that the individual elements 
may control the formation of certain catalytic agents, leads up to the 
question whether the individual elements may not themselves act as 
catalytic agents in certain processes. Such reactions have been more 
graphically worked out for the action of toxic bodies upon protoplasm 
than for the reaction of nutrient substances. 
The results also give evidence to show that the value of an element, or of 
a compound, may consist, in part, in its ability to act as a carrier of certain ions 
or radicals. Magnesium appears to be necessary in some cases for the 
formation of oils. It is not probable that magnesium enters into the 
composition of the oils in any form. It acts rather as a carrier of some 
radical, probably that of phosphoric acid, which is necessary for the 
formation of lecithins. Later these lecithins may be split up with the 
formation of fats. 
Another indirect function which some elements may perform may be 
designated as an ‘antagonistic’ or ‘antidoting’ function. Calcium and 
sodium, for example, appear to be of value in many cases because of their 
power to neutralize or overcome the otherwise harmful effect of magnesium. 
Concerning the real method by which the antidoting is accomplished we 
have little exact knowledge. Judging from the results which have been 
obtained, the beneficial action of these elements seems to be associated 
with biological processes, and the value of any antidoting agent will 
probably vary with different species of plants. It is not out of place, 
however, to note that an extended study of the reactions of the essential 
elements with the products of cellular metabolism might afford data of 
interest in this regard. It is known, for example, that calcium hydroxide 
will precipitate lecithin, but if sodium chloride be present, no precipitation 
will occur. 
In the present paper no attempt has been made to study the value 
of the different essential elements or their compounds as sources of energy. 
A study of that question belongs more properly in the domain of chemistry 
than the present investigation has been carried. The value of the elements 
Q q 
