1726 



CHLOROPLASTS, CHROMOPLASTS AND CHROMATOPLASM CHAP. 37A 



These electron microscope observations were supported by ultracentri- 

 fuge studies (to be described in section 3), also indicating the presence of 

 grana in blue-green algae and purple bacteria. However, just when one 

 may have become inclined to postulate that the grana are universal (and 

 therefore probably indispensable) elements of the photosynthetic appara- 

 tus, complications appeared. 



Steinmann (1952') found in the large, spiral band-shaped chloroplasts 

 of the algae Spirogyra and Mougeofia, fixed in 1% Os04, a lamellar struc- 

 ture extending through the whole chloroplast, without evidence of grana. 



Fig. 37A.13. A circular lamella ("disc") from the granum of a tulip chlorplast, 

 fixed 25 min. in 1% OSO4 and disintegrated by sonic oscillations (after Steinmann 

 19522). Note granulated surface. Compare with Fig. 37A.12. 



Fig. 37A.14. Cross section of u tulip chluroplast fixed for 15 niin. in 1% OsO^, showing 

 laminated grana imbedded in granulated stroma (after Steinmann 19522). 



The lamellar structure is clearly A^isible on longitudinal sections of such fixed 

 Spirogyra chloroplasts (fig. 37A.10). Mougeotia chloroplasts easily dis- 

 integrated into long, narrow bands (fig. 37A.11). By sonic vibrations, 

 these bands could be further disrupted into irregular-shaped patches (fig. 

 37A.12), the thinnest of which were about 7 m/x thick, i. e., of the same 

 thickness as the "discs" in the grana. 



Albertson and Ley on (1954) reproduced a very interesting electron 



