m 



« 



6 



Fig. 6. Micrograph of parts of adjacLiit cells in tapctal layer fourul in anthers 

 of Saiiitpaidia ioimtha. The cytoplasms of the fully differentiated plant cells are 

 richly supplied with elements of the ER. In a way peculiar to these cells, the ER 

 shows some of the features which characterize it in animal cells. Some of the 

 cisternae are lamellar and arranged in groups or clusters. These show the most 

 pronounced association with RNP particles. As in animal cells, these particles show 

 some tendency to form miniature patterns in their distribution on membrane 

 surfaces (arrows). Other vesicles and tubules are essentially free from particles — 

 and most especially those close to the cell surface. Mitochondria [m) are similar to 

 those in animal cells. Otherwise the figure shows proplastids {pp), a few dictyo- 

 somes {d), and some extracellular granules {s). 



The specimen was fixed in OSO4. embedded in Epon 812, and sectioned with a 

 diamond knife. Contrast was improved with lead hydroxide. (Micrograph courtesy 

 Dr. Myron Ledbetter.) 



