20 MISS A. BATESON AND MR. F. DARWIN ON THE EFFECT OF 
Errect oF ACIDS. 
Various acids were tried. As a rule, they had no accelerating 
effect on growth; but caused either retardation or actual contrac- 
tion of the pith. 
6. Effect of Acetic Acid. 
The lower percentages, via. 0'5 per cent. and 1 per cent., had a 
retarding effect. Stronger solutions, viz. 1°6 per cent., 3:2 per 
cent., 3°1 per cent., and 44 per cent., produced no effect. When 
the percentage is raised to 5:4 per cent., the pith contracted after 
10 to 20 minutes, and was killed by the treatment. 
Exp. 20.—Sept. 9, 1886. Jerusalem-Artichoke pith ; lever. 
Times of observation. Rate of “ growth.” Temperature. 
A.M. . à 
11.57 ................. Tap-water in. 17:5 5 
11.595 ............. ses. 158 » à 
12.00 .................. 140 ” a 
1205 ................. 321 » 5 
1207 ................. Siphoned out water. E 
1225 een. Put in 1 per cent. 3 
acetic aeid. » 
12355 ................. 28 » 
12.50 ................. 20 » 
1271 ................ 24 » 
12.85 .................. 25 » 
1211 ................. 16 
Result: retardation. 
Exp. 21.—Sept. 9, 1886. Jerusalem-Artichoke pith ; lever. 
Times of observation. Rate of “growth.” Temperature. 
A.M. C. 
104  ................. 370 c. c. tap-water. 1565 
10.16  .................. 200 » ; 
10.19  .................. 243 » 
10.20  .................. 208 » 
10.22  .................. 161 » 
10.225 .................. 153 » 
10.2255 .................. 1e c. c. acetic acid 165 
'D per cent.). 
1024  ................. pe 72 » 
10245 .................. 62 » 
10.20 .................. 2-2 c. c. acetic acid added  ,, 
(1 per eent.). 
1027  ...............-. 39 » 
10.33  ...............-. 36 17 
10.335 .................. 7°6 c. c. acetic acid added  ,, 
. (81 per cent.). 
1034.5 .................. 32 » 
10.362 ............. Ses 25 
10468 .... c 22 175 
