106 



THE CELL 



In addition, the chlorophyll granules themselves, when under the 

 influence of intense light, alter their shape, becoming smaller and more 

 globular. 



All these occurrences serve to accomplish the same end : 

 " Chlorophyll granules protect themselves by turning on their 

 axes (Mesocarpus), by migration, or by altering their shapes from 

 intense illumination." " If the illumination is weak, the largest 

 surfaces are turned towards the light, in order that as much of it 

 may be received as possible. The behaviour is exactly the oppo- 

 site when the light is strong, a smaller surface being then exposed 

 to the light," 



III. Electrical Stimuli. As has been shown by the experi- 

 ments of Max Schultze (I. 

 29), of Kiihne (IV. 15), of 

 Engelmann, and of Ver- 

 worn (IV. 39), electrical 

 currents, both constant and 

 induced, act as stimuli upon 

 protoplasm, when they flow 

 directly through it. 



If some staminal hairs of 

 Tradescantia (Fig. 53) are 

 placed between non-polar- 

 isable electrodes which are 

 close together, and are then 

 stimulated by means of 

 weak induction shocks, the 

 granular streaming move- 

 ments can be seen to have 

 been influenced in that por- 

 tion of the protoplasmic net 

 through which the current 

 flowed. Irregular masses 

 and globules develop upon 

 the protoplasmic threads ; 

 these separate off at the 

 thinnest places, and become 

 absorbed into neighbouring 

 threads. After a short 

 period of rest, the move- 

 ments recommence, the 



Fig. 53.-^4, B cell of a staminal hair of Tra- 

 descantia virginica. A Normal condition of proto- 

 plasm before it has been disturbed. B The proto- 

 plasm, in consequence of stimulation, has massed 

 itself into balls ; a cell-wall ; b transverse wall of 

 two cells; c, d balls of protoplasm. (After 

 KiiLne; from Ver worn, Fig. 13.) 



