5io Reed . — The Value of Certain Nutritive Elements 
by beryllium, although this element may be absorbed in rather large 
quantities. 
Loew (’92), in discussing the role of magnesium in the plant, set forth 
the hypothesis that one of its functions was to serve as a carrier for 
phosphoric acid. On account of the readiness with which magnesium salts 
are dissociated, they would present the phosphoric acid radical in a form 
favourable for assimilation. The results of numerous analyses can be cited 
to show that magnesium is usually abundant in the plant where nucleo- 
proteid is being formed. If magnesium has such a function, it is evident 
that a small quantity of magnesium could be used for a great deal of work, 
since it may serve repeatedly as a carrier of phosphoric acid to the cell. 
This would also explain such an observation as that of von Raumer, that 
Phaseolus plants were able to grow to a height of one meter when they 
were supplied only with the magnesium stored in the seed. 
Bokorny (’95) practically duplicated Loew’s results upon different 
algae. In addition, he stated that the nuclei of cells which had lived in 
solutions lacking magnesium were smaller than those of the cells in control 
cultures. His observations were principally upon the modifications produced 
in the nuclei and chloroplastids. 
III. The Technique of Experimentation. 
The experimental study described in the following pages was entered 
upon in the year 1904, in the botanical laboratory of the University of 
Missouri. To Professor B. M. Duggar, under whose general oversight this 
investigation has been prosecuted, I wish to extend my heartfelt thanks for 
his uniform kindness in freely giving advice, suggestion, and kindly criticism 
of immeasureable value. Any adequate expression of my indebtedness to 
him is impossible. I wish also to express my sincere gratitude to Professor 
Waldemar Koch for valuable suggestions, and for material which he so 
generously placed at my disposal. 
1. Choice of suitable plants for cultures. 
In choosing material suitable for a study of the action of different 
elements in cell metabolism, I found it desirable to take those plants which 
would admit of microscopical examination in the living condition. For 
certain purposes it was also necessary to employ plants which contained 
a minimum of reserve food substances. With these and other considerations 
in view I have employed different species of filamentous Algae, the protonema 
of moss, the young prothalli of ferns, the root-tips of phanerogamic plants, 
and the filaments of Basidiobolus ranarum . The filamentous thalli of the 
algae could be advantageously studied in the living condition under the 
microscope, and the species of Spirogyra employed were readily fixed 
