1900] CURRENT LITERATURE 423 
the last two salts in our list) the accelerating stimulus is due to the cations, 
and if this be true it could easily have been demonstrated by the use of 
equimolecular solutions of different salts of the same metal. That the effect 
" is not due to the anions we must conclude from the fact that the control solu- 
tions contains SO,-ions from MgSQO,, and NO;-ions from NH,NO, and 
t may be profitable to call attention to the fact that where NaF 
and K,AsO; are used the stimulus to growth must be due not to the cations 
but to the anions. However, the material at hand is far too meager for any 
general conclusions along this line. 
If our author has seemed somewhat easily satisfied as to the chemical 
nature of the stimulus with which he is dealing, the omission is palliated by 
a decided advance which he has made in another line, Heretofore experi- 
ments upon acceleration and retardation of growth have gone no further than 
to determine the relative increase in somatic material. Now, since of the 
materials taken into the plant body some are used to increase its mass and 
others go out again more or less completely oxidized, thus contributing energy 
rather than matter to the organism, it becomes essential to determine whether 
or not accelerated growth means also a relative increase in the amount of 
waste products. Of course in the alge thése products of katabolism take 
the form mainly of COz, and, owing to the photosynthetic process, its amount 
cannot be easily determined. But in fungi we have no such disturbing 
factor. Much of the waste from these fungi comes off in the partially oxid- 
ized form of oxalic acid. The relative amounts of this excreted in the differ- 
ent cases was determined by titration and compared with the amount of 
Sugar taken from the fluid by the growing plants. Relatively much mere 
acid was given off in the normal cultures than in those containing ZnSO,, 
CuSO,, CoSO,, HgCl,, and NaF. For example, with ZnSO,, in twenty-five 
days Aspergillus niger gave off per gram of its own weight 0.443% of acid. 
Without ZnSO, the amount given off was 2.245% per gram of its own weight. 
What are 
called “economic coefficients” are obtained by dividing the amount of sugar 
used by the amount of substance Foti in the plant body. This aaa 
is much greater in the control cultures than in the others. They average ere 
Sone to two, If the weight of the fungus and that of the sugar abso: 
could have been reduced to calories, and then this coefficient found as above, 
it will be seen that it would have been the reciprocal of what, in mechanics, 
would be termed the efficiency. Thus the result above enunc! 
Show at least that the efficiency of the fungus, as 4 machine = gerd 
Up material, increases with the addition of traces of these poisons. 1S 
_ Seems to open up a new method for obtaining some quantita 
_ of the metabolic process. But since the author did not hav 
_ data are not complete enough for this purpose. 
