1354 
It may finally be called to mind that with deficiency of a necessary 
element the metabolism of Aspergillus niger remains unchanged. This 
follows from the amounts found for the plastic aequivalent of the 
carbon. The table shows, namely, that only trifling differences are 
found for all the simultaneous determinations. We see, moreover, 
that those mould layers, which are more developed, possess a corre- 
spondingly lower plastic aequivalent. 
c. Magnesium. Whilst in the study of the other required elements 
it was found that even the slightest quantities cause a perceptible 
growth, magnesium behaves quite otherwise. Relatively great quantities 
(ae er. mol. MgSO, 7 Aq. per L) did not, even after a pro- 
2470000 
longed cultivation, produce any macroscopically perceptible mycelium, 
5) 
whereas stronger concentrations Ga gr.mol. Mg SO, 7 Aq. p. L) 
only after some days caused a considerable growth. 
This result warns us to be cautious in the computation of a 
production in a way as suggested by MrrscHerricH *) even in a rela- 
tively simple ease such as the present. The results of the referring 
experiments are found in Table III. 
The explanation of the above fact has not yet been found. It 
might be supposed that the metabolism of the magnesium is extremely 
slow ; whereas for each individual cell much magnesium should be 
wanted. More acceptable, however, is the supposition that by absence 
or deficiency of magnesium some unknown factor in the medium is 
allowed to exert its noxious influence which may be counteracted 
by addition of more magnesium. Beryllium, lithium, manganese, and 
calcium cannot replace magnesium. (See Table III). Zine can replace 
it, as is shown by the experiments, whose results are exposed in 
Fable LV: 
For cadmium, strontium, and mercury I have not as yet been 
able to find an action analogous to that of zine. Nrs. 12 and 13 
are in particular convincing as they show that even the slightest 
quantities of zinc are sufficient to activate magnesium (0,02 mgr. 
ASO, CHT Ag pl 
The abundant growth in Nrs. 4 and 5 is also remarkable as not 
any magnesium was added there. This does not, however, prove thai 
the magnesium is here replaced by zinc, as it is always possible 
that slight quantities of magnesium are present in the solution, so 
that in this case, too, the influence of the zine may be only an 
9 
2) MirscHERLICH, Bodenkunde fiir Land- und Forstwirte, 2te Aufl. Berlin 1913. 
