218 



MACROMOLECULAR COMPLEXES 



microscopy. In mechanically isolated wall fragments, the scar 

 region (Figs. 8 to 10) gives evidence of morphological differences 

 between outer and inner boundaries of the wall. The scar in Fig. 9, 

 seen from "inside" the cell, appears to be composed of small spheres 

 with dense centers (as seen in GMP-I in Fig. 5), and the plug in 



Fig. 9. Electron micrograph of isolated cell wall of bakers' yeast. Note bud 

 scar as seen from inside cell; mark in center of scar appears as a small papilla. 

 Scale as in Fig. 8. 



the center of the scar appears as a papilla. In Fig. 10, the scar is 

 seen from "outside" the cell, and the mark in the center of the scar 

 appears as a depression. 



On the matter of the existence of different layers in the cell wall 

 of yeasts, Houwink and Kreger ( 1953 ) commented that none of their 

 micrographs provided evidence that the cell wall consists of an inner 

 and an outer layer. However, it should be pointed out that all except 

 their "untreated" specimens were boiled in alkali, and they state, 

 "Boiling with 3% NaOH for three hours, on the assumption that it 

 would prove useful to remove any remaining protein, leaves a 



