CELLULOSE-PROTEIN COMPLEXES J247 



spiral thus produced (and therefore at right angles to the micro- 

 fibrils of this second lamella) and are again preceded by coarse 

 bands appropriately aligned. 



Examination of new lamellae in course of deposition has proved 

 even more critical. The first observations were made on the giant 

 vesicles of Valonia (Preston and Kuvper, 1951; Preston et ah, 1953). 

 The innermost lamella of the wall was stripped off^ by means of 

 Cellotape, and the two types of critical observation made are illus- 

 trated in Figs. 12 and 13. There is no doubt about the latter (Fig. 

 13); it surely illustrates an undisturbed lamella. In the former (Fig. 

 12), however, the new lamella is so delicate that some distortion 

 might have occurred. The impression given is that microfibrils 

 project from a cluster of granules each about 500 A in diameter, and 

 the tentative explanation made at that time was that each cluster 

 represented an "island of synthesis." Microfibrils would then appear 

 to be built by end-svnthesis ( a method of synthesis later supported 

 by Colvin et ah, 1957), association between microfibril and enzyme 

 occurring only at one end. The mechanism of orientation remained 

 obscure, but observations of the tvpe shown in Fig. 13 suggested 

 that orientation occurred in the cytoplasm before the microfibrils 

 of the new lamella were produced. 



More recent observations of Chaetomovpha, using more delicate 

 techniques, are more convincing on this latter point ( Frei and Pres- 

 ton, 1961). In these, the filaments are either fixed directly in an 

 osmium fixative or plasmolyzed in 0.5M sucrose before fixation, but 

 in either case the appearance to be described is the same. The 

 lamellae are then teased off in water, using fine needles under a 

 binocular microscope. Fig. 14 illustrates the type of observation to 

 which attention is now called. This is a frequent but not a constant 

 observation; more frequently the lamella is so densely covered by 

 cytoplasm that no details are visible. Occasionally the lamella is 

 completely free of cytoplasm. Fig. 14 shows clearly, however, ag- 

 gregates of dense granular bodies lying in files on the wall lamella, 

 the long axes of the files lying approximately at right angles to the 

 microfibrils, i.e., in the direction which the fibrils of a new lamella 

 would take. It is to be emphasized that the lamella observed here 



Fig. 13. Electron micrograph of innermost lamella of wall of Valonia ventri- 

 cosa. Granular material, evidently of cytoplasmic origin, has taken up an 

 orientation which the next layer of microfibrils would have adopted. Shadowed 

 Pd-Au. X 22,500. 



