44 life's beginning on the earth 



can be produced on the photographic plate by x-rays which 

 have come in contact with organic material such as a 

 cellulose fiber (Figure 25). Its crystalline nature is thus 

 demonstrated. 







4 



Fig. 25. X-Ray Reflected from a Cellulose Fibek 



The appearance of the peculiar dots and dashes, produced through 

 mutual interference of rays which have passed through very fine openings, 

 indicates crystalline character, as demonstrated in the preceding illustra- 

 tion. Here we have a similar effect from x-rays acting upon a cellulose 

 fiber. The black dots appearing here are, therefore, an indication of the 

 crystallinity of this fiber which is a product of vital growth in a plant. 

 (According to Meyer and Mark.) 



It may be remarked that in this case the rays are not sent 

 through the fiber (Fig. 25) but are reflected from its surface. 

 The reflected rays alternately re-enforce or extinguish each 

 other in much the same manner as the rays which have 

 passed through a crystal. This reflection technique must 



