Contents 



Chapter P^Se 



I. Introduction and Historical Background 1 



The beginnings of cell wall studies. 

 Advances following improved techniques. 

 The modern era. 



II. The Form of the Plant Cell 11 



III. The Chemical Nature of the Constituents of the Secondary 



Wall 21 



Cellulose. 



Hemicelluloses and pectic substances. 



The polyuronides. 



Cellulosans. 

 Lignin. 

 Staining reactions. 



IV. Physical Methods for the Investigation of Structure in 



Plant Cell Walls 31 



Crystal lattices. 



X-ray analysis of plant cells. 



The rotation diagram. 



The unit cell of cellulose. 



The arrangement of glucose residues within the unit cell. 

 Analysis of structure by optical methods. 



Polarized light and structural asymmetry. 



The measurement of refractive indices. 



The interpretation of refractive indices. 



The index ellipsoid 



The use of crossed Nicols. The major extinction position. 



Newton's colour scale. The determination of the m.e.p. 



The significance of path difference. Birefringence. 



Dichroism. 



V. The Structural Features of Cellulose and the Spatial 



Relationships of the Incrusting Substances 71 



The molecular weight of cellulose. 

 The determination of molecular weights: 

 {a) Osmotic pressure determinations. 

 \b)(\) Sedimentation equilibrium. 



(2) Sedimentation velocity. 

 (c) Viscosity determination. 

 Id) Analytical methods. 

 The molecular weight of cellulose and modifications of the 



original Micellar Hypothesis. 

 The Intermicellar System. 

 The distribution of the incrusting substances. 

 Micelle aggregates. The electron microscope. 



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