AND SEA-WEEDS. 
53 
the alga^ the well known sea-weed. The 
former appear in the lower chalky and also in 
the limestones of Paris. The genera of the 
latter vary with the temperature^ some 
tribes flourishing in equatorial seas, and 
others being confined to the arctic zone. 
In the coal mines of Sweden we find the 
Sargassum, which now only comes to us as 
a stray weed from its ocean home in the 
tropics; the amansia^ a form from the tor¬ 
rid zone, and the caulerpa of southern type, 
are discovered in the slates and sands of our 
own country, and the species impressed on 
the Paris limestones are of temperate habi¬ 
tation. Thus we have evidence that the 
depths of some of the ancient seas and rivers 
were decorated with waving foliage like that 
which now imparts beauty to many a soli¬ 
tary bay and lonely strand on the margin 
of the present world of waters. 
II. The second class of plants, the cellular 
cryptogamia, is of little consequence in the 
ancient flora. One or two instances are men¬ 
tioned of mosses being found fossil in the 
upper or tertiary deposits only ; thus by 
their absence harmonizing with other evi- 
E 5 
