532 Reed . — The Value of Certain Nutritive Elements 
4. Experiments upon the role of magnesium. 
Magnesium is needed for the complete development of all plants. 
It is relatively more abundant in the fruits and seeds than in stems and 
leaves. A part of the functions of magnesium appear to be accomplished 
directly, and a part are indirectly performed, as in the case of calcium. 
Magnesium has been assumed by Loew (’ 92 ) to play an important part 
in the assimilation of phosphorus as phosphoric acid. I have found that 
the amount of phosphorus present influences the functioning of the mag- 
nesium and vice versa. 
Since the spores of the mould fungi are quite rich in lecithins and oils , 
they afford a suitable object of experimentation in investigating such ques- 
tions. Some experiments were conducted upon spore formation in Asper- 
gillus niger with the purpose of obtaining some light upon this question. 
It was not possible to exclude entirely the magnesium or the phosphorus 
from these experiments, because an insufficient amount of mycelium would 
have been obtained. The formula for the nutrient solution was that 
used for cultivating Basidiobolus and described on a previous page. No 
agar agar was added since Aspergillus grows well upon the surface of 
a liquid medium. The amount of phosphorus was reduced to fractional 
parts of the normal ratio ; the amount of magnesium was reduced in some 
experiments, and increased in others. 
In the first experiment the phosphorus was reduced to one-fifth the 
normal amount, and the magnesium increased to nearly three times the 
normal, thus making the ratio of magnesium to phosphorus about fifteen 
times as great as in the control solution. The mycelium produced on 
100 cc. of this modified solution was slightly better than that produced on 
the control, weighing 1*55 g- in comparison with 1.20 g. for the control. 
The amount of spore-formation was judged by the eye to be 10 per cent, of 
the control cultures. A second experiment was made to determine the 
effect of decreasing the amount of phosphorus and magnesium present, 
while keeping the ratio equal to that of the control culture. One-tenth the 
normal amount of each element was used. The mycelium which grew on 
this solution produced approximately 50 per cent, as many spores as the 
controls, and approximately five times as many as upon the solutions 
in which magnesium predominated. These results are interpreted to mean 
that the surplus of magnesium in the first experiment was unfavourable to 
the development of spores. The particular point which seems worthy 
of emphasis is that in the first experiment there was twice as much 
phosphorus present as in the second ; yet, on account of the great pre- 
dominance of magnesium, conditions were not so favourable for spore- 
formation as in the second experiment. In other words the maintenance 
