TS'O 



157 



Fig. 1. Electron micrograph of a freeze-dry preparation of microsomal particles from pea 

 seedlings. Magnification 41,000 X; thorium shadowed with an angle of 6.5:1. 



may vary during the different phases of cell growth and differentiation. Pre- 

 liminary information suggesting that this is so has been reported in this meet- 

 ing: information concerning rapidly growing cells, such as those of yeast and 

 bacteria. Eventually, then, studies of structure of particles in the steady state 

 will evolve into studies of structure of particles through a life cycle. 



Processes or agents that remove or substitute divalent ions from the particles 

 promote dissociation of the particles. For instance, in a 0.8 per cent particle 

 solution, in pH 6.5, 0.025 p, phosphate buffer, there is only 6 per cent dissocia- 



