DEPARTMENT OF MARINE BIOLOGY. 



239 



he designates as the blaze current) and points out the variations of electrical 

 conductivity in tissues at different stages of maturity and the great increase of 

 conductivity which often takes place consequent to electrical stimulation; this 

 increase, he surmises, is "partly due to the multiplication of electrolytes by 

 dissociation." 



COKDTJCTIVITY AND BlAZE CURRENTS IN HyMENOCALLIS. 



Series of observations made on leaves still attached to the plant show that 

 the conductivity changes not only after electrical excitation, but that it varies 

 at different times, owing to the action of natural conditions. 



Further, in nearly all the cases observed by me, the blaze current {i. e., elec- 

 trical response to direct electrical excitation) is larger when the conductivity 

 is low than when it is high. These changes may be realized by studying the 

 table below, which gives the results of a typical experiment. 



Leaf 60 cm. long; plant about to flower; electrodes 20 cm. from tip, 2 cm. apart, applied 

 longitudinally in center of ventral surface. Electrical stimuli used, always of equal 

 strength but fairly weak. 



The above figures show that after 21 hours of darkness the conductivity 

 has increased more than tenfold. After half a day's exposure to sun and rain 

 the conductivity has again become low. On the other hand, the blaze response 

 is vastly augmented after exposure. 



It is possible that, expressed as volts, the last response is too high, a fallacy 

 which might be produced, if there is a sudden increase of conductivity on 

 initiation of the blaze-current. Leads at four other levels on this leaf gave 

 similar variations of conductivity and response. The direction of the response 

 may be the same as that of the stimulating current, or opposite, away from 

 the leaf-base, or towards it. 



Not all leaves gave such regular variations, nor did this leaf at a later 

 stage; but I wish to repeat the experiments, avoiding disturbance to roots, 

 gradual death of leaf, and other complicating factors. 



Remarks. 



My experiments indicate that light (rather than rain or temperature) has an influence on 

 the subsequent electrical state of leaves. Dr. Waller's system of blaze currents (if I under- 

 stand it) might off'er some such explanation for the phenomena as the following: 

 Light — photosynthesis — condensation of electrolytes — decreased conductivity — storage of 



combustible material — increased power of response. 

 Dark — respiration predominant — increase of electrolytes — increase of conductivity — 

 expenditure of combustible material — decreased power of response. 



Perhaps it may be possible to test out some such hypothesis as this by means of chemical 

 as well as electrical tests. 



Dr. Shiro Tashiro and I have made experiments, using his delicate tests for carbon dioxide, 

 in an attempt to obtain quantitative correlation between blaze response and the state of 

 respiration. Practical difficulties, however, are considerable, and our results have not yet 

 reached a stage for publication. — A. G. M. 



