Electrical Response in Cotton Plants . 109 
(a) Method of Control, consisting in duplication of electrodesand leads, 
with examination of test-subject and a control alternately throughout. 
(b) Method of Balance, being an alternating connexion of text-subject 
and control in series or in parallel, with consequent augmentation or 
neutralization of the response. 
My thanks are due to Dr. Wilson, of the Cairo School of Medicine, 
for advice and interest, to my colleague, Mr. F. Hughes, for the loan 
of the Post Office box, and to Professor A. D. Waller for kindly and 
stringent criticisms on the manuscript of this note. 
TABLES SHOWING TYPICAL RESULTS. 
Two components are given for each tissue tested, namely, the resis- 
tance in ohms, and the value of the response as millimetres deflexion of the 
galvanometer. 
The testing was in all cases done in duplicate, with a control on the 
same switchboard. The value of the response is given in pairs; thus 
in Table II the readings run : 
A. 134, 62 : 41, 34 : 34, 24 : 13, 6 : -16, -23. 
C. 88, 54 : 39, 42 : 35, 28 : 30, 15 : - 9, - 21. 
These imply that an antidrome shock on A gave 134; during the 
recovery of A an antidrome shock on C gave 88 ; the primary circuit was 
then reversed and A was tested again with a homodrome shock, giving 
63 mm. deflexion, and then B gave 54 with the same treatment. This 
succession continues to the end of the row of figures. 
In all cases the interval between stimuli was only so long as was 
required for the previous response to die down. Correction is made for 
slight displacements of the circuit zero through injury currents. 
Four response readings or more were usually taken when the initial 
one amounted to more than 10 mm. deflexion. 
Table I. 
Response from various parts of similar field plants at different hours 
of the day : 
Upper line = response. Lower line = resistance. 
Portion tested . Time . 
Noon . 
10 p . m . 
7 a . in . 
Root 10 cm. 
8, 10 : 
67, 50 : 35 , 4 8 = 
below soil- surface 
190,000 
115,000 
Hypocotyl-root 
45 > 40 : 55 , 65 : 
' 50 , 53 : 45 , 50 : 
55 , 50 : 40, 3 8 : 
junction 
300,000 
1 20,000 
— 
First leaf 
1, 4 : 
2, 5 : 
20, 17 : 
midrib 
370,000 
300,000 
320,000 
Fifth leaf 
9, 10 : 
3 , 6 : 
1°, 3 : 
midrib 
200,000 
300,000 
Fifth leaf 
9, 8: 
12, 18 : 
5 , 3 : 
petiole 
250,000 
300,000 
600,000 
Y oungest leaf, 
8, 9 : 
9 , 23 = 25, 11 : 
0* 
O 
C* 
CO 
i. e. 10th leaf 
170,000 
180,000 
— 
Youngest internodes 
20, 15 : 12,18: 
56, 25 : 27, 55: 
85, 110 : 99, 98 
of stem. 
120,000 
110,000 
7 5, ooo 
