524 Physiologie. 



are facultative anaerobes, and may exhibit slow Streaming for 

 6 — 8 weeks in the absence of free oxygen. No special chemical 

 changes are connected with Streaming. 



Of the constituents of the cell, cellulose, albumin and 

 Chlorophyll are paramagnetic: starch, sugar, oil, water and 

 probably myosin, are diamagnetic. Plant-cells usually, though 

 not always, place their long axes parallel to the lines of force 

 in a magnetic field. The strongest magnetic force used exercised 

 little or no direct effect on Streaming, although a pronounced 

 secondary effect is produced after long exposure as the result 

 of inductive action. 



The minimal, optimal and maximal temperatures for 

 Streaming vary according to the plant or cell examined, and 

 depend upon the age or condition, the external medium, the 

 duration of exposure, the supply of oxygen, the rapidity with 

 which the temperature is raised or lowered. In the case of 

 facultative anaerobes, the response to changes of temperature 

 is less pronounced in the absence than in the presence of oxygen. 



Strong light retards Streaming, while weak light may in- 

 directly acceierate it in chlorophyllous cells. Mechanical distur- 

 bances may act as inhibitory Stimuli, and may be propagated 

 internally in the form of pressure-waves. 



Food-materials exercise both a direct and an indirect effect 

 upon Streaming. Acids, alkalies and metallic poisons all retard 

 Streaming, and may cause a temporary shock-stoppage when 

 suddenly applied. Alcohols and anasthetics when dilute may 

 acceierate Streaming, but when more concentrated always retard 

 it. Those alkaloids that are strong nerve or muscle poisons 

 have relatively little action on Streaming. 



Weak electrical currents may acceierate, strong ones always 

 retard, Streaming, while sudden shocks produce a temporary 

 arrest. Cells are more sensitive to electrical Stimuli at moderately 

 high temperatures than at very low or very high ones, and the 

 nucleus is fatally affected before the cytoplasm. 



The only kind of energy which appears capable of producing 

 Streaming movements under the conditions existing in plant- 

 cells is surface-tension energy; and this is probably brought 

 into play by the action of electrical currents which traverse the 

 moving layers and are maintained by chemical action in the 

 substance of the protoplasm. These currents may act upon 

 more or less regularly arranged bipolar particles of emulsionised 

 protoplasm in such a manner as to reduce their surface-tension 

 on the anterior side, or increase it on the posterior side, hence 

 producing Streaming movement in a definite direction. 



Vines (Oxford). 



KOSAROFF, P., Untersuchungen über die Wasserauf- 

 nahme der Pflanzen. (Beihefte zum botanischen Central- 

 blatt. 1902. Bd. XII. p. 293.) 



