256 FINE-STRUCTURE OF PROTOPLASM II 



some scepticism. However, gold-stained chloroplasts in profile clearly 

 exhibited dichroism (cf. p. 84, loi), which is indicative of a laminar 

 texture (Menke and Kuster, 1938). 



Further proof of the lamellar texture was provided by the large 

 chloroplasts oi Anthoceros, that classical object which, at the instigation 

 of Ernst, had already been appealed to so fruitfully in the dispute 

 over the relationship between plastids and chondriosomes (Scherrer, 

 1 9 14). Menke and Koydl (1939) identified layers at the limit of 

 microscopic resolution in cross-sections through the chloroplasts of 

 Anthoceros using the enhanced resolving power of the UV microscope. 

 Not only do the big chloroplasts without grana of Anthoceros and 

 the Conjugatae algae appear to be laminated, but also the granulated 

 chloroplasts {Selaginella, Phaseolus). The grana are united by thin 

 lamellae, which induced Menke (i94od) to devise the plan of Fig. 

 130b of a section through the discoid chloroplasts of the higher plants. 

 The pile-like arrangement of the grana (Strugger, 1950, 195 1) is 

 clearly visible. 



Electron microscopy (Kausche and Rusk a, 1940; Menke, 1940 a; 

 Algera, Beyer, v. Iterson, Karstens and Thung, 1947; Granick 

 and Porter, 1947). Besides stroma and grana, a distinct boundary 

 layer has been disclosed (Frey-Wyssling and Muhlethaler, 1949a) 

 as a third morphological element of the chloroplast (Fig. 1 3 la, p. 259). 

 This layer must consist essentially of proteins, as it displays the 

 properties of a solid and does not show any sign of the liquid or semi- 

 liquid state characteristic of lipid matter. It is probable that the living 

 boundary contains lipids, but their amount must be small as compared 

 with the total lipid mass in the chloroplast. Obviously they join the 

 emigrating myelin. The proteins of this plastid layer must be of 

 the fibrous type ; otherwise the formation of a membrane would not 

 be possible when dried. The formation of strands of stretched chloro- 

 plasts (Kuster, 1935c) is probably due to this protein. How much 

 the dried membrane differs from its natural state in the living chloro- 

 plast is not known. 



Under the membrane, the grana are visible as discs. The stroma, on 

 the other hand, does not show any conspicuous structure. Wyckoff 

 (1949) has given evidence of globular macromolecules about 250- 

 300 A in diameter, which lie on and between the grana. If the plastid 

 membrane has burst, as usually occurs during the preparation of the 



