Chapter VI —55— The Plastids 



ments, which those who hold this opinion think are caused ex- 

 clusively by cytoplasmic currents. From observations of WEISS, 

 SCHIMPER, and Kuster it appears that chloroplasts are capable of 

 becoming distorted and of showing amoeboid movements. This is 

 also recorded for leucoplasts, as will be seen later. Now Sau- 

 VAGEAU showed by observations of seedlings of Saccorhiza bulbosa 

 that when exposed to intense light the chloroplasts, during their 

 movements, present contractions and dilations which can be ex- 

 plained only by movements which they make themselves. Senn, 

 who recognizes the capacity of chloroplasts to move themselves, 

 attributes this to the presence of a cytoplasmic sheath surrounding 

 them which he calls a peristromium. This, according to Senn, 

 gives rise to pseudopodia which permit the chloroplasts to change 

 shape and place. The existence of this peristromium, however, has 

 never been confirmed and remains very problematical. 



