3 CHLOROPLASTS 257 



chloroplasts, the whole carrier film is sprinkled with these globular 

 bodies (Fig. 131c, d). This behaviour would indicate that the stroma 

 is a corpuscular dispersion of macromolecules, i.e., a sol. Since a sol 

 has no framework, the characteristic shape of the chloroplast must be 

 due to its membrane, much the same as in erythrocytes, and to its 

 internal lamination (Fig. 130b). The chloroplast can change its shape 

 (Senn, 1908), or even form processes (Heitz, 1952); this faculty 

 must also be ascribed to the membrane, which may be compared with 

 the ectoplasm of creeping protozoa. This again argues in favour of 

 a protein rather than of a lipid ground mass of the plastid membrane. 

 The grana supporting lamellae suggested by Menke (Fig. 130b) 

 and Strugger (195 i) have not yet been found in the electron micro- 

 scope. 



We may ask whether the macromolecules found by Wyckoff 

 (1949) represent lipo-proteins or only proteins. It is almost certain 

 that the latter is the case. The preparations show very thin flat discs 

 (Kausche and Ruska, 1940) of various diameters up to 5 // and only 

 100-200 A thick. It can be shown that before desiccation these discs 

 wxre in a semi-liquid state. They never have folds, as the plastid 

 membrane has, and dry perfectly smoothly on the carrier film, even 

 if they include isolated grana (Fig. 131c). There has been much dis- 

 cussion on the nature of these discs. They have been looked upon as 

 protein lamellae (Menke, 1940a) or phosphatide bladders (Algera 

 and co-workers, 1947) (which is unlikely, as the chloroplast contains 

 only 0.5-2.5% of phosphatides), but there is no doubt that they 

 represent the total lipid matter of the chloroplast and must be con- 

 sidered as myelin forms. Fig. 131c shows how this myelin flows out 

 of a fraction of a disintegrated chloroplast. 



It is likely that the grana lipids have also emigrated, because, as 

 seen in the electron microscope, the grana consist of proteins only. 

 Washing with lipo-solvents does not alter them (Menke, 1940 a; 

 Granick and Porter, 1947). They seem to be layered Hke a low pile 

 of coins. Occasionally such a pile appears to be overturned (Fig. 

 13 id), when a number of very thin lamellae, all of the same diameter, 

 are visible. The question is justified, whether these lamellae are really 

 lamellar parts of grana or perhaps ghosts of whole grana. However, 

 Steinmann has disclosed in Aspidistra chloroplasts as many as 30 of 

 these lamellae in the same pile (unpublished). This rules out any 



