424 Horne and Williamson .— The Morphology and 
retardation. The divergence of the curves, however, is not so easily 
explained; the effect seems to be due to the toxicity of the acids in 
question. 
(d) The growth-rate is least in the citric acid culture, the reverse of 
the result obtained with E. viridescens. 
G. Colour Production in Media containing Gallic or Tannic Acid. 
During the course of the experimental work with acids, it was observed 
that cultures of E. viridescens in potato extract agar, containing gallic or 
tannic acid in o*i and 0*25 per cent, concentrations, exhibited a deep green 
colour in the substratum. In work carried out concurrently coloration was 
obtained with numerous fungi when grown in solutions containing 02 per 
cent, gallic acid. The colour is in some cases not due, or not entirely due 
to acid, since certain fungi, e. g. species of Fusarium , produce colours in the 
presence of carbohydrate. Other fungi—for example, a species of Botrytis — 
u 
produce a reddish brown substratum in gallic and tannic acid potato extract 
plate cultures. A similar colour, which is dark olive green when diluted 
with water, appears after two days when the same Botrytis is kept at 20° C. 
in solutions containing gallic acid at a 0-2 per cent, concentration, and 
K 3 P 0 4 and MgS 0 4 (1*25 grm. and 0-75 grm. respectively per litre). In this 
case the oxidation of gallic acid takes place through enzymatic action. 
Again, solutions of gallic acid undergo oxidation when alkali is present in 
excess, with the ultimate production of purpurogallol, which is of a brownish 
olive colour (in dilute solution). Hence, if compounds of nitrogen are 
present in media containing gallic acid, liquid coloration might ensue 
through the liberation of ammonia owing to fungal activity. For these 
reasons, the following series of media were prepared, containing members 
from which compounds of nitrogen and carbohydrate respectively were 
omitted: 
j. K 3 P 0 4 , 1*25 grm.; MgS 0 4 , 0-75 grm.; asparagin, 2 grm.; glucose, 
2 grm. per litre. 
2. As in No. 1, with glucose omitted. 
3. As in No. 1, with asparagin omitted. 
4. As in No. 1, with both glucose and asparagin omitted. 
To each of these, 10 c.c. of a 2 per cent, solution of sterile gallic acid 
were added after autoclaving. Flasks (capacity 250 c.c.), containing 100 c.c. 
of liquid (pale yellow in colour), were inoculated with the three species of 
Eidamia , and these, together with the necessary controls, were kept at 20° C. 
With E. acremonioides no growth was obtained in solution 1 after two 
days and the experiment was discontinued. In the case of E. catemdata 
and E. viridescens colour appeared in the solutions containing asparagin. 
