440 



CHAPTER L. 



PRE-CAKBONIFEROUS FLORAS. 



Cambrian Plants. — The Laurentian and Huronian deposits 

 have as yet yielded no remains of plants ; but the occurrence 

 of graphite in large quantity in the former of these would 

 strongly support the view tliat the Laurentian period was 

 not without an abundant marine vegetation. The Lower 

 Cambrian rocks have yielded many so-called " fucoids ; " but 

 these are almost invariably to be referred to the tracks and 

 l)urrows of marine worms. The only generally admitted plant 

 of the Lower Cambrian period is the Foj^hi/ton (fig. 696) 

 of the " Fucoidal Sandstone " of Sweden. 



The singular fossils referred to this genus consist of 

 straight, furrowed, and striated stems, winch can hardly be 

 anything else than the remains of plants. The affinities, 

 however, of these ancient fossils are quite undetermined, 

 except that it seems pretty certain that they cannot be 

 referred to the Algw ; and Principal Dawson is disposed to 

 regard them as perhaps of inorganic origin. 



In the Upper Cambrian rocks (I'otsdam Sandstone) of 

 North America occur various so-called " Fucoids " {Pala'o- 

 pliycus, &c.) The true nature of these, however, is in many 

 cases very doubtful, and it is questionable if any of them 

 can really be regarded as plants. 



Silukian Plants. — The remains of plants in the Silurian 

 series are comparatively few in number, and require little 

 consideration. In the Lower Silurian rocks a large number 

 of fossils have been regarded as Sea-weeds, and referred to 



