SUMMARY OF RESULTS 121 



facultative anaerobes, and may exhibit slow streaming for six to eight 

 weeks in the entire absence of free oxygen. 



No special chemical changes are connected with streaming. 



Of the different constituents of the cell, cellulose, albumin, and chloro- 

 phyll are paramagnetic, starch, sugar, oil, water, and probably myosin 

 also are diamagnetic. Plant-cells usually, though not always, place their 

 long axis parallel to the lines of force in a magnetic field. 



The strongest magnetic field used exercised little or no direct effect 

 on streaming, although a pronounced secondary effect is produced on 

 prolonged exposure as the result of inductive action. 



The connexion between certain forms of streaming movement and 

 metabolism is a wholly indirect one, but this can hardly be a general rule. 



Indirect relationships exist between streaming, growth, and assimilation, 

 but no direct ones. Similarly the nucleus exercises no direct but a pro- 

 nounced indirect influence on streaming. 



An organized arrangement of the protoplasmic particles is probably 

 an essential condition for regular continuous streaming. A great variety 

 of agencies when suddenly applied seem to disturb this arrangement 

 momentarily, and hence produce a temporary cessation of streaming. 

 This shock-effect results from sudden changes of concentration, rapid 

 falls or rises of temperature, momentary electrical excitation, and the 

 sudden application of various poisons. 



The minimal, optimal, and maximal temperatures for streaming vary 

 according to the plant or cell examined, and also depend upon (i) the 

 age or condition ; (2) the external medium ; (3) the duration of the 

 exposure ; (4) the supply of oxygen ; (5) the' rapidity with which the tem- 

 perature is raised or lowered. 



At temperatures above 30 C. the velocity immediately assumed is, 

 in the absence of a shock-effect, always greater than that shown a few 

 hours or a few minutes afterwards. Between ioC. and 30 C. the per- 

 manent velocity is immediately or almost immediately assumed. Below 

 10 C. the acceleration due to a rise of temperature frequently does not 

 become fully manifest until after a certain lapse of time. 



In the case of facultative anaerobes, the response to changes of 

 temperature is less pronounced in the absence of oxygen than in its 

 presence. With short exposures, the optimum and maximum points are 

 raised, but with prolonged ones the maximum point is lowered by the 

 absence of oxygen. 



Strong light retards streaming, while weak light may indirectly 

 accelerate it in chlorophyllous cells. It is still doubtful whether streaming 

 is affected by directly impinging electro-magnetic wave vibrations other 

 than those of light. Mechanical disturbances may act as inhibitory stimuli, 

 and may be propagated internally in the form of pressure waves. 



