X THE MOLECULAR ARCHITECTURE OF PLANT CELL WALLS 



VI. Wall Structure in Thick Cell Walls. The Green Algae 91 



,. Introduction 

 Valonia 

 The X-ray diagram. 



Striation direction and chain orientation. 

 <i The organization of the wall as a whole. 

 The filamentous algae. 



Group 1 . Cladophora, Chaetomorpha, Rhizoclonium, etc. 

 Group 2. Halicystis, Hydrodictyon, etc. 



VII. Wall Structure in Thick Cell Walls. Flowering Plants 113 



Layering in xylem cells. 



The m.e.p. of conifer tracheids. 



The X-ray diagram of conifer wood. The spiral diagram. 



Crossed fibrillar structure in tracheids and fibres. 



Structure in other mature cell types. 



Vessel elements. 



Collenchyma cells. 



Cotton hairs. 



VIII. Structural Variations in Homologous Cells 152 



Dimensional relationships in tracheids and fibres. 



The development of conifer tracheids. 



Variation of spiral angle with tracheid length. 

 Dimensional relationships in bamboo fibres. 

 Relationships in other fibrous cells. 



\X. The Primary Wall of Growing Cells 170 



The chemical nature of the primary wall. 



Cellulose. 



Pectin, hemicelluloses and cellulosans. 



Protein. 



Other substances. 

 The X-ray diagram of primary walls. 

 Crystallinity in primary walls. 

 Orientation of cellulose in primary walls. 



X. The Mechanisms of Orientation and Growth 182 



The invariate orientation during growth. 



Spiral growth in the sporangiophores oi Phy corny ces. 



Wall structure and cell shape. 



Osmotic forces in growth. 



The cellulose-protein complex in growing walls. 



The mechanism of orientation and the growth process. 



Bibliography 203 



Index 207 



