Electrical Response in Cotton Plants. 107 
one electrode on the stem near the seed-leaf stalks and the other nearer the 
ground, the former point was always ‘ zincative 5 in the beginning. 
Currents of injury . — With ordinary care in handling the material the 
current of injury was insignificant, and all the experiments were, in fact, 
conducted without the use of a compensating current. The exception to 
this was provided by the tender tissues of the apical bud and youngest 
internodes of the stem. In these the injury current was frequently of fair 
magnitude and of some hours’ duration. 
Fatigue. — Using the moderate induction shock already mentioned, it 
was found that a very definite fatigue, or progressive numbing of the 
response, was exhibited, ending in a reversal of polarity in the tissue 
(Table IV]. Some attempts were made to ascertain whether the form of 
this fatigue-curve could be in any way utilized, but without result. Atten- 
tion was also directed to a possibility that the weakness of root-responses 
might be due to the employment of too powerful a stimulus, but no indica- 
tion of such an effect was obtained ; the absence of a sledge-coil hampered 
this inquiry. 
Similarity of plants at various times of the day. — The physiological 
condition of cotton plants in Egypt at dawn, at noon, and at midnight are 
so extraordinarily different, especially in May and June , 1 that they might 
be expected to show some difference in electrical response. Comparable 
plants removed from the field at these times, and immediately tested in 
various parts, showed no clear differentiation (Table I), excepting that the 
terminal bud (which at noon is not growing) gave feebler responses in the 
middle of the day. Even this result was not constant. 
Immersion of the root-system in water. — Comparable pots of seedlings 
of the same age were tested, whereof one pot had been immersed in water 
over the soil surface for varying periods, while the other was watered as 
usual. The first pair of pots tested over a period of four days gave definite 
results (Table III), showing deterioration of the blaze-current from the 
water-logged pot, beginning at the root-hypocotyl junction and moving 
upward to the first and second internodes. The result was, however, 
fallacious ; for instance, the second pair tested reversed this behaviour by 
giving markedly stronger blazes at all times from the water-logged pot. 
These water-logged plants showed that they were not in normal health, in 
spite of their free responses, by subsequently shedding their lower leaves. 
Desiccation. — Pots of seedlings were allowed to dry up and tested 
against controls. Two days before their death the blaze from them was 
scarcely inferior to that from the controls (Table IV), when they were unable 
to stand erect and when some were only just able to recover on watering. 
1 The author: The Cotton Plant in Egypt. London, 1912. 
