12 OF THE DIATOMACE.E. 



In any case lie is tolerably sure to come across good speci- 

 mens of other Cryptogamic orders. 



The fact that the separate valves of the Diatomaceae are 

 protected by an almost indestructible coating of silica, 

 allows of their being recognised years after the organism 

 itself has ceased to exist, as may be seen in almost any 

 dried-up pool. Nay, countless ages may pass away, and 

 still the valves, on being brought to the light of day, will 

 exhibit their delicate markings as clearly as though the 

 hand of the Creator had sculptured them but yester- 

 day. Numerous deposits of these peculiar Alga? are to be 

 found in different parts of the world. It is sufficient to 

 mention San Fiore in Tuscany, Franzenbad in Bohemia, 

 and Berlin, as well-known examples. This remarkable 

 quality of endurance naturally leads us to look for traces 

 of their presence in localities where we should not usually 

 search for the Algse. Guano, for instance, is rich in 

 beautiful forms. Dwellers by the seaside may furnish 

 themselves with numerous species, which vegetate in the 

 unknown depths of the ocean, by a microscopic examina- 

 tion of the contents of the stomachs of fishes, mollusks, 

 and medusa? ; a task not much to the taste perhaps of the 

 beginner, but one which we would recommend him to 

 undertake boldly, as he is sure to meet with a rich 

 return. 



So minute are the Diatomaceaa, that, with few excep- 

 tions, individuals escape the eye of the collector altogether, 

 save when armed with a microscope or powerful lens. 

 Still he should never hesitate to carry off a supply of what 

 may, at first sight, appear to be worthless matter. For 

 oftentimes he will find examples of most interesting species 

 in gatherings which, to the naked eye, seem entirely desti- 

 tute of vegetation, and, for the sake of these, he must be 

 content to draw a few blanks in the vegetable lottery. 



It is rare, indeed, to find DiatomaceaB in any quantity 

 free from admixture with other members of the Alga?, and 

 uncontaminated by mud and sandy particles. Generally 



