398 Bayliss. — On the Galvanotropism of Roots. 
application of acid or alkali, when examined microscopically, also showed 
a tendency in the cell walls to elongate radially. 1 
io. Rate of Growth of Stimulated Roots. 
From time to time measurements were taken to see whether the 
normal rate of growth was disturbed by stimulation. The average rate 
of growth per hour during the twenty-four hours preceding stimulation was 
taken, and also during the twenty- four hours following it and during the 
next day : the results showed stimulation was followed by retardation. 
The following measurements illustrate this : — 
Phaseolus multiflorus 
Vicia Faba 
Vicia Faba 
Phaseolus multiflorus 
Rate per hour dur- 
ing 2 4 hours before 
stimulation. 
•44 mm. 
•14 „■ 
*3 J 
Rate per hour 24 
hours after stimu- 
lation. 
•24 mm . 
•06 „ 
•25 „ 
•49 » 
Rate per hour 24 
hours later still. 
•42 mm . 
•23 » 
*04 „ 
•17 » 
In many cases where no curvature took place after stimulation there 
was a complete stoppage of growth. That growth took place on both 
sides of the root was readily seen by covering the root after stimulation 
with a thick layer of Indian ink, and observing the cracks which formed on 
the concave as well as on the convex side of the curved root. 
By using a horizontal measuring microscope, and taking periodical 
observations, the rates of growth on both sides of the curving root were 
more accurately measured. The readings were taken during the two or 
three hours preceding stimulation, and then continued for three or four 
hours. 
During the first and second hour or longer after stimulation, when 
prolonged weak currents were used, there was usually an acceleration 
of growth on both sides of the curve ; but it was greater, and lasted longer, 
on the convex side. Ultimately growth was retarded, if not quite checked, 
on both sides of the root. 
10 a. Diagrammatic Representation of the Growth in 
Length of Curving Roots. 
The following diagrams are selected from many to give an illustration 
of the curves of growth usually obtained. The three black lines to each 
figure except Figs. 6 and 7 represent the curves of the three apical zones 
marked out on each root, each zone of about 1*5 mm. length : the red line 
represents a general curve made by regarding the three zones as one. 
Each cm. length on the base line represents a period of one hour, and a cm. 
length on the ordinate line a unit of increment in length. The asterisks 
1 The question of these abnormal thickenings is being made a subject for further study. 
