BLAZE-CURRENTS OF VEGETABLE TISSUES. 41 
The ivy petiole is comparatively sluggish; the geranium petiole 
is comparatively lively. Under similar conditions, the response 
or blaze of the former is below 41, volt, while that of the latter 
is upwards of 45, volt. 
$19. Turg» Day.—Some of the questions asked in $ 15 require 
to be answered, and I shall make use of peas for the purpose. 
Peas in their pod afford us an unlimited supply of individual 
test-objects, similar, and protected from accidental injury. 
The relation between strength of excitation and strength of 
blaze-current, and the time-relations of the latter, are easily 
examined. The observations have to be made in a systematic 
and leisurely fashion; so I have reserved them for a wet day, 
offering no external temptations. 
Fig. 3.—Pxa (Pisum sativum). Excitation by a single break induction-shock 
from A to B.  Blaze-current from A to B, i. e. homodrome. 
1 1 1 | 1 fi L L | 1 L 1 ji 
0 ! 2 3 4 5 10 minutes. 
The ordinates are in scale-divisions of 1 cm.; with the resistance in circuit, 
each 1 cm. indicated an approximate voltage=1/1000 volt. 
§ 20. The observation of each individual blaze-current requires 
5, 10, or 15 minutes, according to its strength. A blaze aroused 
too soon after a previous blaze is smaller than normal. One 
should allow the zero to be recovered of itself, and not impa- 
tiently return to a false zero by manipulating the compensator. 
