1742 



CHLOROPLASTS, CHROMOPLASTS AND CHROMATOPLASM CHAP. 37A 



With osmic acid as fixative, the peak corresponded to a weak positive double 

 refraction; with Zenker's sohition, to no double refraction at all (fig. 

 37A.21). The authors suggested that osmic acid fixes both proteins and 

 Hpides, while Zenker's fluid fixes proteins only. If the negative morphic 





"2 



^ <P /<o ,0 ,<o .O /> 



>■ <0 <o to <b 'v 'V 



-V- ^ -^ \ \ N^ V, 



Fig. 37A.21. Double refraction of Mougeotia chloroplasts as a function of 

 imbibition (after Frey-Wyssling and Steinmann 1948): ( — ■) fixed with Zenker 

 fluid, imbibed with acetone 4- CH2I2; (- -) fixed with OSO4 + HgCla, imbibed with 

 acetone + CH.I). Ordinate, retardation (r) in mn; abscissa, refractive index. 

 Hi, of the imbibing fluid. 



double refraction is due to protein lamellae, and the negative intrinsic 

 double refraction to an array of lipides in the lipide layers, the different ef- 

 fect of the two fixatives is easily explained. 



5. Composition of Chloroplasts 



(a) Proteins, Lipids and Nucleotides 



Timm (1943) obtained some additional data concerning the protein 

 content of the chloroplast and the cytoplasm in leaves (of. Vol. I, p. 371). 



