728 FLOEA OF THE PKIMAEY OR PALEOZOIC PERIOD. 



Marine algae ; including the lower Permian, Silurian, and Cambrian 

 rocks. 2. The Eeign of Vascular Cryptogams. 



Williamson thinks that these divisions of Brongniart cannot be 

 adhered to. He finds that there are fossU plants which show an 

 evident transition from the Vascular Cryptogams to the Gymnosperm- 

 ous Exogens, and that these divisions cannot be separated as regards 

 fossil plants. He suggests the division of Vascular Cryptogams into 

 two : — 1. An Exogenous group, including LycopodiacesB, Equisetacese, 

 and the fossU Calamitacese. 2. An Endogenous group, containing the 

 Perns. The former uniting the Cryptogams with the Exogens through 

 the Cycadacese and Ooniferse ; and the latter linking them with the 

 Endogens through the Palmse. 



I.— FLOKA OF THE PEIMAEY OK PALEOZOIC 

 PERIOD. 



Reign of Aceogens. 



(According to Beongniaet.) 



In this period' Acrogens and Gymnosperms are found to have 

 existed simultaneously, the former predominating over the latter in 

 number and size. The number of the Fern family, the great develop- 

 ment of the Lycopodiacese and Equisetacese, are the most prominent 

 characters of this epoch. Other anomalous families belonging to the 

 Gymnosperms are also met with, which diflfer from actually existing 

 orders. 



Floea of the Silueian and Oambeian Systems. — In the 

 lower Palseozoic strata the plants which have been detected are few. 

 In the Silurian and Cambrian systems we meet with the remains of 

 ancient marine plants, as well as a few terrestrial species. Even in 

 the still older Laurentian rocks, if the remarkable structure known as 

 Eozoon canadense be considered, as it generally is, an animal, the ex- 

 istence of contemporary plants may be inferred, inasmuch as without 

 vegetable life animals could not obtain food. In the Lower SUurian 

 or Grauwacke, near Girvan, Hugh Miller has found a species resem- 

 bling Zostera in form and appearance. In the Lower Old Red 

 Sandstone of Scotland, he has detected Fucoids, a Lepidodendrou, 

 and Lignite with a distinct Coniferous structure resembling that of 

 Araucaria, besides a remarkable pinnate frond. In the middle Old 

 Red of Forfarshire, as seen in the Arbroath pavement, he has col- 

 lected specimens of a peculiar plant, bearing organs which resemble 

 in appearance small receptacles of Nelumbium, besides a Fern with 

 reniform pinnae and a Lepidodendrou ; while, in the Upper Old Red, 

 near Dunse, a Neuropteris, like N. gigantea of the Coal-measures, 



