1724 



CHLOROPLASTS, CHROMOPLASTS AND CHROMATOPLASM CHAP. 37a 



lipide material. When the latter is extracted by solvents, or oozes out in the 

 drying process, the discs become loosened, the granum sags, and occasion- 

 ally overturns, scattering the protein discs over the film. 



Fig. 37A.10. Cross section through Spirogyra chlorophist fixed for 10 min. in 1% OsOj, 

 showing disintegration into band-shaped hmiinae (aftei' Steinniann 1952>j. 



Fig. 37A.11. Cross section through Mougeotia chloroplast, fixed for 45 min. in 1% OSO4, 

 showing disintegration into band-shaped laminae (after Steinmann 1952^). 



The much larger, also thin, non-folded structures, usually round or o\'al, 

 but occasionally streaky or fibrous (Vatter 1952, and Thomas et al. 1952, cf. 

 fig. 37A.9), were interpreted by Frey-Wyssling as dried-out residues of 

 lipide drops. Most of these large myelin "pancakes" lie free on the film, but 

 some seem to protrude from grana, like ham slices from a sandwich. This 

 supports Frey-Wyssling's suggestion that some "myelin" material origi- 



