ELECTRON MICROSCOPY 



1721 



Weier's conclusion (Vol. I, chapter 14) that they contain much Upide ma- 

 terial. In Granick's shadowed preparations, the leached grana were scarcely 

 distinguishable from the matrix. What remains of the grana after leaching 

 probably consists of proteins, about as dense as those which form the ma- 

 trix. Granick and Porter estimated, from these obser\-ations, that less than 

 one-half of the grana material is proteidic. 



Fig. 37 \. 7. Electron micrograph of macromolecules in stroma of a maize 

 chloroplast isolated in methanol. The size of the macromolecules varies from 

 less than 10 m^ to more than 50 lUfj, depending on the solvent or buffer in which 

 the jjlastids were isolated (after Vatter 1952). 



So-called "grana" preparations, obtained l)y Granick and Porter, ac- 

 cordmg to Aronoff's prescriptions {cf. Chapter 35, page 1556), showed, 

 under the electron microscope, mostly fragmented chloroplasts in which 

 clusters of grana were still embedded in matrix material. Whether the 

 presence of the latter — which is difficult to remove altogether — is essential 

 for the Hill reaction, is an interesting cjuestion. 



Algera, Beijer, van Iterson, Karstens and Thung (1947) obtained micro- 

 photographs very similar to those of Granick and Porter, and showing some 

 details in greater clarity. They used tulip leaves, ground in a mincer while 

 sodium carbonate solution was added dropwise to a pB. of 6.0. After pas- 

 sing through cheesecloth, the opalescent suspension was centrifuged at 3000 



