2$4 



FINE-STRUCTURE OF PROTOPLASM 



II 



view is, on the contrary, isotropic. Given these facts, either the entire 

 chloroplasts, or the single grana must be optically uniaxial with 

 negative birefringence. 



It can be shown that the birefringence of the big chloroplasts in 



Fig. 129. Layer birefringence of chloroplasts of Mougeotia (from Frey-Wyssling and 

 Steinmann, 1948). Abscissa: refractive index nj of the imbibition liquid. Ordinate: 



retardation T in m/<. 



Conjugatae algae is a form birefringence (Frey-Wyssling and Stein- 

 mann, 1948). The flat chloroplasts of the 2Xg2.MoMgeotia were used for 

 this study. They have the shape of a rather thick plate which is as 

 long and wide as the whole cell in which it is located. Further, they 

 appear homogeneous in the light microscope, no grana having been 



