399 
Bayliss . — On the Galvanotropism of Roots . 
mark the time at which a strong current (4-5 volts) was passed for three 
minutes ; or, in curves where two appear, the period during which a weak 
current (1-5 volts R 100,000 ohms.) was passing. 
The signs -f and — indicate the sides of the root touched by the 
+ or — electrode. 
In each case the lines on the left-hand side indicate the concave side 
of the curve, and on the right the convex. 
In Figs. 6 and 7 the curves represent the growth in length of the root 
as indicated merely by change in the position of the root-tip. 
11. Experiments with Acid and Alkali diffusing through 
Gelatine. 
Lilienfeld 1 has recently published some experiments of tropic responses 
induced by different salt solutions in radicles growing in gelatine. No 
very definite results were obtained, and in some cases they were even con- 
tradictory ; yet a few might well be classed as of an ordinary chemotropic 
nature. 
With a view to seeing whether there was any analogy between these 
curvatures, especially those produced by acid and alkaline solutions, and 
the curvature due to an electric current, similar experiments in a slightly 
modified form were made. 
Seedlings were grown in a round glass vessel about 12 cms. wide con- 
taining a neutral solution of agar (5 or 6 per cent.) from the centre of which 
a small rod (-5 cm. diameter) of the jelly had been cut out, and the hole 
thus made was plugged with a roll of blotting-paper which was moistened 
with the solution to be tested, either H 2 S 0 4 , NaHO, or sodium carbonate 
N 
of — or other strength, or phosphoric acid neutralized by KHO. In some 
instances the solid jelly was stirred up to ensure better aeration. Each 
experiment lasted about two days, during which time the blotting-paper 
was moistened several times. The atmosphere above the seedlings was 
kept damp and well aerated. A few of these experiments were carried out 
on a clinostat. 
No definite results were obtained, probably because the method was 
incapable of proper control, diffusion taking place too rapidly to allow 
of one side of the root perceiving and responding to the stimulus before its 
whole surface was equally affected. An attempt to secure slower diffusion 
was made by plugging the stem of a very small thistle funnel with blotting- 
paper, and inserting it in the gelatine instead of the usual roll, but with no 
satisfactory results. 
Lilienfeld, Ber. d. Deutsch. Bot. Gesellsch., March, 1905. 
