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320 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
gators have reported the presence of oxalic acid resulting from 
the growth of both fungi and bacteria, but unfortunately much 
of this work is of little value, because methods of analysis are 
not given. The detection of this acid by some methods is very 
unsatisfactory. 
A few years after de Bary's work, Wehmer (54) published an 
extensive series of articles on this subject. He studied a number 
of fungi (mostly saprophytic) with reference to oxalic acid excre- 
tion, and of these he found Aspergillus to be the most active and 
Penicillium next, and, therefore, he confined his studies to these 
two fungi. Some of the factors concerned in the production of 
oxalie acid or its salts, aecording to Wehmer, may be summed 
up here: (1) A large yield of oxalic acid is not produced in the 
presence of free organic or inorganic acids, not being found in 
the medium when free acids exceeded 0.2-0.3 per cent, while, 
on the other hand, it can be formed in the presence of as much 
as 2-3 per cent of the salts of these acids. (2) The sources of 
nitrogen are very important, for the amount of the oxalie acid 
produced varies aecording to the kind and quantity of nitrog- 
enous compounds supplied. (3) Abundant oxalie acid forma- 
tion is favored by the addition of some basie phosphate, or at 
least some compound with which the acid can combine to form 
a soluble salt. (4) The effect of light or darkness on oxalie 
acid formation is inappreciable. (5) Temperature is an influ- 
encing factor in oxalate production, for the latter is inhibited by 
a high temperature, the temperature for a maximum oxalate 
production being, in fact, very near the minimum for the growth 
of the organism. 
Wehmer's analytical method consisted in precipitating out 
the oxalic acid, or its soluble oxalate, as the calcium salt, which 
was filtered off, dried to a constant weight, and weighed. Al- 
though this method is perhaps as well suited for this purpose 
as any other reported, it is open to criticism. А detailed dis- 
cussion, however, will not be given here. 
Wehmer holds that oxalic acid is a type of excretion, and that 
it is in some way connected with respiration, that is, with CO; 
elimination. Не considers that the variability in the amount of 
oxalie acid produced is due to its use in the metabolism of the 
fungus. Emmerling (20), in his contribution to this subject, 
