OBSERVATION BY RHEOTOME ON ELECTRIC RESPONSE 45 



while in the first of these the recovery was completed in 

 fifteen seconds, in the latter, even after the lapse of forty 

 seconds, it was still far from complete. Indeed, in this case 

 it was not altogether accomplished till after several minutes. 

 The character of the tissue again is an important factor in 

 determining the time required for recovery. Thus it will be 

 shown that in a vegetable structure functioning as nerve, 

 recovery is much more rapid than in ordinary tissue. The 

 physiological modification induced by season, moreover, is 

 seen in the fact that response and recovery are quicker in 



FIG. 35. Response of (a) quickly reacting Amaranth ; 

 ih\ of sliicrcris}i Colnrasirt. 



of sluggish Colocasia 



summer than in winter. This difference is demonstrated by 

 mechanical response also, for in that of the leaf of Mimosa, 

 as already stated, it is found that, whereas in summer the 

 period is six minutes, in winter it is as long as eighteen, or 

 three times as much. 



In the study of the time-relations of response, we may 

 overcome the difficulty of the galvanometer-inertia by using, 

 as already said, some modification of the rheotome, originally 

 devised by Bernstein. The relative values of electrical 

 variation induced at various periods after .the impact of 

 the excitatory shock may here be found by making brief 



