28 THE MOLECULAR ARCHITECTURE OF PLANT CELL WALLS 



attached the side chains IV, V or VI. It appears further that in the lignin 

 from Angiospenns only III is present, while in Gymnosperms I and II 

 are involved, demonstrating yet another chemical difference between 

 these two large groups of plants. The structures shown in Fig. 9 are. 



OCH, 



H 



H-C-OH 

 I 



H-C-OH 



H-C-OH 

 I 



IS 



H-C = 



H-C-H 

 I 



H-C-OH 



CH, 



c=o 



I 



H-C-OH 

 I 



n 



H-C-H 

 H-C-OH 



H-C 



OCH, 



H 



H-C-OH 



I 

 H-C-OH 



I 

 H-C-OH 



OCH, 



Fig. 9. For explanation, see text. 



of course, only the units of which lignin is composed, and it remains 

 still to be settled in what way these units are linked together. Freuden- 

 berg himself suggests that lignin in the wall may be considered as a 

 product resulting from the etherification and subsequent condensation 

 of the above units, to produce complexes such as A in Fig. 9. These, 

 and the corresponding products from II and V, III and VI, are supposed 

 to undergo further etherification and condensation by means of which 



