94 



PHYSIOLOGY OF STREAMING MOVEMENTS 



the latent period of recovery, they do so to a very incommensurate extent, 

 and the period seems sometimes to fluctuate independently of them. 



Similar results were obtained with CJiara, Vallisneria, and Elodea, 

 except that these plants, and especially the last named, are able to 

 withstand somewhat higher temperatures. 



The direct effect of a constant current is to lower the optimal and 

 maximal temperatures for streaming, so that at low temperatures the action 

 of a weak constant current is usually to accelerate streaming. Stronger 

 currents, however, retard it from the outset, and hence antagonize the 

 accelerating influence of a rise of temperature. In this case streaming 



is more rapid under the conjoint in- 

 fluence of a moderate rise of tem- 

 perature and of a moderately strong 

 current, than when the latter only is 

 applied, but is slower than when only 

 the rise of temperature conies into 

 play. If currents are used which cause 

 only a temporary shock-stoppage, or 

 none at all when slowly applied, the 

 usual effect is to lower the maximal 

 temperature by from 4 to 5 C. with 

 short periods of exposure. But if 

 stronger currents are used and the 

 duration of the exposure prolonged, 

 streaming may ultimately cease as 

 much as 10 C. below the usual maxi- 



FIG. ii. Hot stage, arranged for electrical excitation. 



mal point (viz. 40-44 C. instead of 46-52 C.), although when exposed 

 to similar currents the same length of time at from i8-25C. streaming 

 remained active, and in some cases became even more active than before. 



SECTION .41. Induction Currents. 



Induced alternating currents gave similar results, except that the 

 immediate action is more marked owing to the greater intensity of the 

 currents and their more rapid rise and fall. Weak induction shocks cause 

 slow streaming to become more active, and may excite it in Elodea and 

 Vattisneria. Strong induction shocks cause in all cases a temporary or 

 permanent stoppage. As the temperature rises to from 35 C. to 40 C., 

 the recovery and recommencement of streaming take place more rapidly, 

 but above these temperatures more slowly, in spite of the steady increase 

 in the respiratory activity. 



Similarly as the temperature rises above 20 C. the minimal intensity 

 for a shock-stoppage is lessened, so that the primary and secondary coils 



