Physiology of the Genus Eidamia . . 423 
(, a ) The curves for the control and acids practically coincide ; the acids 
have exercised no appreciable effect on growth. 
(b) After the second day, the growth-rate in each case is .fairly uniform, 
as evidenced by the almost straight lines. 
(( c ) After the fifth day the curves diverge, indicating that the growth- 
rate is no longer uniform, and slightly decreased in the case of malic acid, 
tartaric acid, and the control. The retardation experienced coincides with 
a lowering of the hydrogen-ion concentration, but since the control was 
initially pH 7, and it is unlikely that the acid-containing media would 
Fig. 23. E. viridescens. Growth on potato extract agar with N/50 solution of various acids. 
exhibit greater alkalinity than the control, this retardation appears to be 
due to some other factor. 
II. E. catenulata (Fig. 22) (pH range of the media relatively unfavour¬ 
able to growth). 
(a) The curve for the control (initially pH 7) falls below those for 
the acids. 
(b) The curves for the acids diverge sharply after the third day, the 
gallic acid culture exhibiting the maximum growth-rate. 
(c) The curves for citric and tartaric acids become depressed after the 
third and fourth days respectively. E. catenulata is highly tolerant of acid, 
hence the lowering of the hydrogen-ion concentration should cause growth 
