PLATE V 



Fig. 1. Comparison of the X-ray diagrams of Cladophora 

 cultured under constant illumination and under normal 

 light-dark alternations. Photographic details as in 



Plate II, fig. 3. 

 Upper right, lower left: light-dark alternation. 

 Upper left, lower right: continuous illumination. 



Fig. 2. X-ray diagram of a bundle of parallel cells of 

 Hydrodictyon. Beam perpendicular to cell length, CuKa 

 radiation. Note (1) the presence of complete circular arcs 

 demonstrates random orientation. (2)^ the inner circle 

 corresponding to a spacing of about 7-4 A., suggests clearly 

 the presence of cellulose II instead of cellulose I. 



[Facing p. 112 



