SEA-WEEDS. 
173 
The fossil botany of the algae is very in¬ 
complete^ and we may expect that future re¬ 
searches will considerably extend the meagre 
list of present discoveries in this department 
of phytology. 
The following description given by Mrs. 
Somerville of the marine vegetation of the 
existing seas should stimulate the geologist 
to ascertain to what extent the deep oceans 
inhabited by the spirifers and ammonites of 
early eras, and the mediaeval shallows 
wherein the saurian floated, may have ex¬ 
hibited similar fields. 
Sea-weeds adhere firmly to the rocks 
before their fructification, but they are easily 
detached afterwards, which accounts for 
some of the vast fields of floating weeds; 
but others, of gigantic size and wide distri¬ 
bution, are supposed to grow unattached in 
the water itself. There are permanent 
bands of sea-weed in our British Channel 
and in the North Sea, of the kind called 
Fucus Filum, which grow abundantly on the 
western coasts of the Channel, and they lie 
in the direction of the currents, in beds 
15 or 20 miles long and not more than 
p 5 
