432 CONNECTICUT EXPERIMENT STATION REPORT, I912. 
low as 0.2 per cent. in case of var. parasitica, the growth of the 
fungus causes a darkening of the medium. This indicates an 
oxidation of the tannic acid by the fungus, since these tubes 
without the introduction of the fungus remain undarkened 
except with the higher percentages, when they color as soon as 
made, upon cooling. With E. gyrosa, this darkening scarcely 
takes place, and with var. parasitica is less evident in those 
tubes containing only 0.2 and 0.4 per cent. of tannic acid, but 
shows on all strengths above these with both fungi about the 
same, though appearing sooner with var. parasitica. 
(2) The medium in the tannic acid tubes remains liquefied 
when 0.8 per cent. or more tannic acid is added. The acidity 
of potato-juice agar and, in the lower percentages, of tannic acid 
potato-juice agar, where darkening of the medium does not 
interfere, can be tested before and after growth of these fungi 
by titrating with x Na O H, using phenolphthalein as an indi- 
cator. These tests show that after E. gyrosa or var. parasitica 
has fully developed in plain potato-juice agar the acidity is 
practically unchanged; but in tannic acid potato-juice agar both 
of these fungi cause a lowering in the acidity of the medium, 
and the higher the acidity usually the greater the loss, though 
not proportionately greater, as shown by the following tests: 
Tannic Acid Acid Test Acid Test Loss in 
added (per cent.). before inoculation. after growth. Acidity. 
N N 
0.0 0.15 cc. — Na O H 0.15 cc. — NaOH 0.0 
20 20 
0.2 Ae) Bl oe ce ce ce 0.4 ce ce ce ce ee 0.5 
0.4 1.2 ce oe ce oe oe 0.85 sé ce “oe oe ee 0.35 
0.8 I g ee “se ce ac “e ce ee ee ce oe 
1.2 2.1 cc ee ini se oe 1.4 ae ae ae ce “ce 0.7 
1.6 2.7 “6 ce sé ce ce 1.8 “ae “sé ce “e ee 0.9 
(3) Cultures of E. gyrosa var. parasitica containing 0.2, 0.4; 
0.8 per cent. tannic acid show a more vigorous spore develop- 
ment than the check cultures of potato-juice agar without tannic 
acid. The same was true of E. gyrosa regarding mycelial 
development, but to a less extent, and possibly also as to spore 
development, though with this fungus the spores do not exude 
very abundantly in any case. 
(4) At about 4 per cent. the loss in color, especially with E. 
gyrosa, becomes quite evident. In the liquefied tubes up to 
