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 role of primary importance in the economy of 

 marine life and one of great geological interest. 



The distribution of Alga3 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 Algae 

 have been described by Brongniart, Saporta, and 

 other palaaophytologists, under such names as Fucites, 

 Chondrites, Cowfervites, Caulerpites, &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 Algae is in the Devonian, from which 

 Mr. Carruthers has described Ncmatopliycus, an Alga 

 of siphoneous structure ; and Sir Joseph Hooker 

 Pachytheca, of more doubtful affinity as yet. With 

 the exception of a fossil Caulcrpa from the Kimme- 



