236 MACROMOLECULAR COMPLEXES 



Fig. 5. Electron diffraction diagram of Valonia cellulose; orientation correct 

 for comparison with Fig. 4. 



shaw et al. (1958) have shown that the microfibrils themselves 

 usually contain sugars other than glucose, and some of the results 

 of these analyses are presented in Table 1. These fully confirm the 

 opinion, which has been gaining ground for a number of years, that 

 cellulose is a mixed polysaccharide. With two species (Valonia and 

 Cladophora) and possibly a third (Chaetomorpha) (Table 1), 

 sugars other than glucose have not been detected. The cellulose 

 involved appears to be a "true" substance in the strict chemical and 

 crystallographic sense, and it has been suggested that it should be 

 distinguished as eucellidose (Myers and Preston, 1959). The struc- 

 ture proposed for cellulose microfibrils is illustrated in Fig. 6. This 

 represents diagrammatically a transverse section of a microfibril 

 (Preston and Cronshaw, 1958; Preston, 1958). The short oblique 

 lines represent the projection of chain molecules in this plane. The 

 central core, represented as a lattice, is crystalline and is surrounded 

 by a cortex in which the arrangement of the chains is less regular. 

 Within this cortex occur chains of glucose residues ( solid lines ) and 

 of other sugars ( broken hues ) . These may be aggregated together 

 to form larger groups, within which the microfibrils are still dis- 

 tinguishable. This has led Frey-Wyssling (1959) to refer to the 

 single structures as elementary fibrils and to the aggregates as micro- 



