504 Reed . — The Value of Certain Nutritive Elements 
of sodium to the plant may be settled. They seem to point quite con- 
clusively toward a possible utilization of sodium by the plant. 
2. Previous work upon the role of phosphorus. 
Ville (’61) appears to have been one of the first investigators to show 
conclusively that phosphorus is necessary for all plant-growth. Although 
his experiments were performed with sand cultures they show such definite 
results that there can be no doubt of his conclusions. He also showed 
that, in order to serve as a plant nutrient, the phosphorus must be in the 
form of phosphates. 
Stoklasa (’96) and Molisch (’96) refuted the statements made by 
Bouilhac ( 94) regarding the possible substitution of arsenic for phosphorus. 
The first-named investigator showed that such a substitution was im- 
possible for phanerogams, the second confirmed the evidence for certain Algae. 
Berthelot and Andre (’88) studied the amounts of phosphorus in 
Amarantus caudatus at different times during the growing season, finding 
that the relative content of phosphorus was greatest in the young plant, 
and decreased continually to maturity. Although it is universally held 
that phosphorus in the form of inorganic or organic compounds is necessary 
for the growth of any plant cell, little knowledge is at hand concerning the 
role of phosphorus in the cell. Loew (’91) described the pathological 
conditions ensuing when Spirogyra cells were deprived of phosphorus. 
The cells studied ceased to grow although they continued for some time 
to form starch and proteid ; the chloroplasts turned yellow, and fats and 
proteids accumulated in the cells. He also pointed out the importance of 
phosphorus for the formation of lecithin. He regarded lecithin as a body 
into which fat must be changed in order to become combustible in the 
protoplasm. 
Becquerel (’04) found that moss spores would germinate and grow for 
about a month in nutrient solutions lacking phosphorus, but the protonema 
gradually lost its green colour and died. 
Schoene (’06) reported the results of experiments upon the germination 
of moss spores in nutrient solutions lacking phosphorus. He observed 
that after sowing spores upon such deficient solutions that the oil content 
of the spore disappeared, and at the same time there were formed rod- 
shaped chlorophyll bodies. In Funaria the oil globules disappeared as 
the protonema developed. The more rapid the formation of starch, the 
more rapidly did the oil content vanish. 
3. Previous work upon the role of calcium. 
Aside from the earlier ideas upon the value and function of nitrogen 
in the plant, the first ideas upon the specific functions of any one of the 
mineral nutrients appear to have been those of W. Wolf ('64). That 
