20 SEAWEEDS 
Though the pelagic flora is most imperfectly 
known as regards its constituent elements, it is 
manifest that its extent is enormously in excess 
of the coast marine flora so much more highly 
diversified in its forms, and that it consequently 
plays a 7éle of primary importance in the economy of 
marine life and one of great geological interest. 
The distribution of Alge in time, as made known 
to us by their fossil remains, is a branch of study 
which is somewhat starved by the lack of material. 
A considerable number of so-called fossil Algz 
have been described by Brongniart, Saporta, and 
other paleophytologists, under such names as Fucites, 
Chondrites, Confervites, Cawlerpites, &c., with no better 
evidence of their algal nature than what may be 
suggested by the outlines of markings. On the 
other hand, Nathorst has obtained very general 
support for his denial of the algal nature of such 
markings, which he ascribes to trails of animals and 
other casual impressions in many cases. After weed- 
ing out these forms, and trusting only to such cases 
as exhibit microscopic structure, or characteristic 
casts in the round supported by evidence derived from 
geology as to the nature of the bed, or at the least 
very unequivocal impressions in beds of undoubted 
marine origin, there is very little left to be 
chronicled in the testimony of the rocks. The first 
appearance of Algz is in the Devonian, from which 
Mr. Carruthers has described Nematophycus, an Alga 
of siphoneous structure; and Sir Joseph Hooker 
Pachytheca, of more doubtful affinity as yet. With 
the exception of a fossil Caulerpa from the Kimme- 
