Electron micrograph 
shows the folds of the 
endoplasmic reticulum 
thickly dotted with tiny 
dark bodies, the 
ribosomes. 
29 
Drawings show both the 
ribosome-covered rough 
endoplasmic reticulum 
( top ) and the ribosome- 
free smooth endoplasmic 
reticulum (bottom). 
