540 Reed . — The Value of Certain Nutritive Elements 
magnesium and phosphorus were present in the ratio of the normal culture 
solution. An excess of magnesium over phosphorus was detrimental to 
spore formation. 
14. Magnesium salts were necessary for the continued health and 
activity of the chloroplasts. 
1 5. Oil was not formed in Vaucheria when grown in the absence of 
magnesium. 
16. The nuclei of Spirogyra were able to divide mitotically when no 
magnesium salts were furnished, although the process was somewhat 
retarded. 
1 7. The essential elements studied appear to function in two ways: — 
(a) as component parts of cell structures or fluids ; and (b) as indirect agents 
in causing less understood physical or chemical conditions necessary for the 
proper functioning of the cell, whether as carriers of other ions, or as 
specific antidoting agents. 
18. The non-living parts of the cell, e. g. cell-wall, starch granules, or 
oil globules, are the only ones visibly modified by the lack of an essential 
element. The strictly living portions of the cell did not manifest any 
morphological changes until they were killed. 
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