526 Reed . — The Value of Certain NtUritive Elements 
phosphorus in the same manner as described in the experiments where 
potassium was absent. 
A large culture of Spirogyra , which had grown for thirty-five days in 
the absence of phosphorus was subjected to a temperature of 5 0 C. during 
the night. At 9 the next morning it was placed in good light at 
a temperature of about 20° C. Two hours later it was examined with 
a microscope to ascertain what effect the lack of phosphorus would have 
upon the processes of nuclear and cell division. 
• It was evident from the first that the tendency to divide was manifested 
by fewer cells than in experiments where only potassium was absent. The 
filaments in the phosphorus-free solutions were in a living condition, yet 
a comparatively small number of cells showed any elongation or growth of 
the cells similar to that noted in cultures where potassium was absent. 
This may have been due either to a lack of suitable materials for growth, 
or, what is more likely, to the lack of simpler soluble substances, which 
by their reactions could have supplied the energy necessary for mitosis. 
The few cells which showed a tendency to divide had elongated to 
approximately twice their length. The nuclei also were attenuated in 
the direction of the longer axis of the cell, but there were no cases of 
division to be found, although at the same time there were a great many 
dividing cells in the control cultures. Three and one-half hours after 
taking the material from the low temperature, I divided the material in 
which no mitoses were occurring into two portions. One portion was kept 
unaltered for a control, to the other I added a few drops of a 2 per cent, 
solution of potassium phosphate. At the end of an hour the material was 
examined, and I found that the addition of the phosphorus had enabled 
some of the cells, which had been previously stimulated, to accomplish the 
process of division. The culture to which no potassium phosphate had 
been added showed no cases of mitotic divisions. 
On the whole the experiments go to establish the predominating 
importance of phosphorus for the metabolism of the cell. When, for 
example, spores containing a small amount of reserve materials were put 
into a solution lacking phosphorus they were not able to germinate. 
When living cells were transferred to phosphorus-free solutions they soon 
ceased to grow. When cells succeed in living for a time in the phosphorus- 
free solutions their metabolism is impaired, and abnormal products are 
formed. 
3. Experiments upon the role of calcium. 
Most green plants, except certain of the Cyanophyceae, appear to 
require a suitable supply of calcium for normal growth. Relatively small 
amounts of calcium appear to suffice for the nutrition of most plants. It 
will not be safe to make such, broad claims for the necessity of calcium in 
