400 Bayliss . — On the Ga Ivanotropis m of Roots . 
Similar experiments were carried out using troughs of sand, silver 
or coarse red, the salt solution being placed at one end of the trough 
in a little cubical chamber, of which the side facing the seedlings was made 
of plaster of paris. 
In these experiments also the results were very conflicting. Some 
rather better results were obtained when using two plugged thistle funnels 
containing, respectively, decinormal solutions of NaHO and H 2 S 0 4 , and 
placed 10 to I2cms. apart, with the seedlings in rows between them ; the 
gelatine being coloured with phenolphthalein so that the extent of diffusion 
might be traced. 
On the whole this series of experiments gave no conclusive results. 
Possibly the lack of aeration in gelatine delayed the curvatures until 
diffusion had gone too far ; while in the troughs of sand the drainage and 
other currents may have been too rapid to allow of any difference of 
concentration being maintained on opposite sides. 
The direct application of acid and alkali, however, on opposite sides 
gave very decided and consistent results. 1 
12. Summary of Results. 
From the details which have been given there is enough evidence 
to connect these galvanotropic curvatures with those of a chemotropic 
character — the chemical stimuli being here the acid and alkaline ions 
formed during electrolysis. 
In support of this view the following facts may be summarized : — 
1. Acids and alkalies are formed in appreciable quantities at the 
places where the + and — electrodes touch the roots. (Section 6.) 
2. Similar curvatures to galvanotropic ones are produced by acids and 
alkalies placed on the sensitive zone of the root. (Section 6.) 
3. If a piece of root tissue under a + or — electrode be cut out 
and applied to another root, the latter curves to the acid or alkaline tissue. 
(Section 6 .) 
4. Acids and alkalies applied to the sensitive zone of roots can produce 
signs of injury similar to those produced by an electric current. (Sections 
8 and 9.) 
5. When one electrode is placed flat against the apex, and the other at 
some distance beyond the elongating zone of the root, there is no curvature : 
in this case the acid or alkali is produced in the root cap, and by diffusion 
affects the sensitive zone equally in all directions, and hence there is no 
differential response. But if the hinder electrode is on the sensitive zone, 
usually the root curves to this electrode, but sometimes remains straight, 
1 In the research as carried out, the experiments with seedlings grown in gelatine (section 3) were 
consequent upon this series of observations. 
