CELLULOSE-PROTEIN COMPLEXES 241 



Electron Microscope Observations 

 of Cell Wall-Cytoplasmic Relations 



There is thus some evidence that cellulose and protein may be 

 associated in plants just as they are now known to be in animal skin. 

 We come now to the electron microscope evidence which seems 

 convincing. 



Electron microscope evidence for the interpenetration of walls 

 and the proteins of cytoplasm comes from many sources. Miihle- 

 thaler ( 1950 ) was the first to show that in primary walls the cellu- 

 lose microfibrils are twisted round each other, and to state clearly 

 that this could not happen if the wall and cytoplasm were separated 

 by an interface. Similar observations can be made even with sec- 

 ondary walls, and the walls of the seaweeds Valonia, Cladophora, 

 and Chaetomorpha have proved to be particularly revealing (Frei 

 and Preston, 1961). 



In these three species, microfibrillar orientation reaches its most 

 perfect state. The walls consist of many lamellae, each normally one 

 or two microfibrils thick, and each consisting of a compact set of 

 parallel microfibrils. These microfibrils lie, moreover, with the 

 planes of 6.1- A spacing (Fig. 2) more or less parallel to the wall. 

 The microfibril direction alternates from one lamella to the next 

 through an angle which can be as low as 60° but is usually rather 

 less than a right angle so that odd lamellae show one orientation and 

 even lamellae the other. In Valonia, in some Cladophora spp., and 

 in some Chaetomorpha spp. (but not all), a third orientation also 

 occurs, much more rarely than the other two. A model of the whole 

 wall of a Valonia vesicle is illustrated in Fig. 9 ( Cronshaw and Pres- 

 ton, 1958 ) . This regular alternation from one direction to the other, 

 through an angle which is not the same from point to point in a cell, 

 cannot be ascribed to twinning. It must reflect changes in the pro- 

 teins at the surface of the cytoplasm, and recalls the somewhat simi- 

 lar arrangement of protein fibrils found in the cuticle of earthworm 

 by Rudall and Reed ( see Astbury, 1949 ) . In all lamellae, however, 

 the microfibrils are frequently twisted around each other. Moreover, 

 the switch from one orientation to the other is never clean and 

 abrupt. Microfibrils from one lamella may pass through the next 

 lamella and become part of the next-but-one lamella with the same 

 orientation; microfibrils from one lamella may interweave with those 



