8o PHYSIOLOGY OF STREAMING MOVEMENTS 



operated more injuriously than a permanent acidity or alkalinity. For 

 example, streaming ceased in a cell of Char a after nine hours in o-i per 

 cent. KHO, and after one hour in o-i per cent, tartaric acid, whereas if the 

 two ends of a cell were immersed in similar solutions of acid and alkali 

 respectively, streaming ceased in five to six minutes. Similar results were 

 obtained by the author with Chara and Nitella, the central portion of each 

 cell being sheathed in vaseline so as to prevent the possibility of the cell 

 forming part of an electrical circuit. A rapid stoppage occurring in from 

 ten seconds to two minutes is simply the result of a shock-effect, as the 

 alkaline protoplasm from one end of the cell is suddenly permeated with 

 acid at the other. In such cases, momentary streaming may occur generally 

 or locally, but the power of streaming is permanently lost within four to 

 twelve minutes. More dilute solutions exercise no perceptible shock-effect, 

 however suddenly applied, but here also a cell permanently loses the power 

 of streaming (when its ends are in acid and alkali respectively) in T V tn to 

 Y^o-th the time required when entirely immersed in one liquid. This is 

 undoubtedly because the protoplasm is unable to accommodate itself with 

 sufficient rapidity to the changes from acid to alkali, and from alkali to 

 acid, whereas in either of the above media, taken singly, a certain amount 

 of accommodation is possible. 



Streaming may be completely arrested in Elodea and Vallisneria by 

 eight to sixteen hours' immersal in 01 per cent, solution of normal ammo- 

 nium carbonate, without the power of recovery being lost in all cases. 

 After six to ten hours' immersal in the same strength of solution, slow 

 creeping streaming is shown only in a few of the older cells of Chara and 

 Nitella, and none in the younger ones. Streaming does not commence or 

 become distinctly active until after three hours in those cells which ulti- 

 mately recover, although when tested by the Bacterium method they may 

 exhibit a power of CO^-assimilation an hour previously in some cases, but 

 in others still none. 



After prolonged immersal in a dilute alkaline solution, the slowly 

 streaming protoplasm usually becomes extremely vacuolated, and accord- 

 ing to Klemm 1 the vacuoles arise, owing to the fact that the alkali 

 converts certain insoluble constituents of the protoplasm (microsomes) into 

 soluble and highly osmotic substances. These absorb water from the cell- 

 sap and form vacuoles. That some such change occurs is certain, but it is 

 not necessarily due to any direct solvent action of the alkali, for dilute 

 solutions of caffein, which acts not as a solvent but as a precipitant 2 , pro- 

 duce a similar vacuolation of the protoplasm. Both dilute acid and dilute 

 alkali convert coagulable albumin into the non-coagulable acid- and alkali- 

 albumins, but dilute acid acts on living protoplasm very differently, and 



1 1. c., p. 42. a cf pfgffer, Physiology of Plants, Clar. Press, 1900, Vol. I, p. 68. 



