12 
OF THE DIATOMACE.E. 
In any case he is tolerably sure to come across good speci- 
mens of other Cryptogamic orders. 
The fact that the separate valves of the Diatomacese 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 Alga?. 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 medusae ; 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 Diatomacea?, 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 Diatomacese in any quantity 
free from admixture with other members of the Alga?, and 
uncontaminated by mud and sandy particles. Generally 
