THE BEGINNINGS OF PLANT LIFE n 



the faintest indications of their fascinating sculp- 

 turings are visible. 



The refined nature of some of the markings of 

 diatom valves defied the powers of the best 

 microscopes for many years, and even with the 

 finest of modern lenses most skilful manipulation 

 is required to bring out their details of structure. 

 In fact, the more delicate forms are used by the 

 makers of microscopes for testing the accuracy 

 of their work. 



A very remarkable fact regarding these minute 

 sculpturings is that frequently, as the magnify- 

 ing power is increased, new and unsuspected 

 details of structure become visible. What were 

 minute rows of dot-like spaces reveal, when 

 enormously magnified, other perforations and 

 sculpturings within them of equal beauty and 

 symmetry. 



And, when we have exhausted the powers of 

 our best optical instruments, who knows what lies 

 beyond? If unsuspected marvels of fascinating 

 minuteness have been revealed with the advance 

 of modern instruments, one cannot help wondering 

 where this decoration ends. The methods by 

 which these tiny plants construct their almost in- 

 destructible shells defies all attempts to explain ; 

 and in saying "almost indestructible" I am well 

 within the mark, for these silicious frustules, or 



