165 



vegetable life are very rare, though afibrcliug undoubted 

 evidence of' the; existence of these three classes. In the 

 Carboniferous "system, the Acrogens and Gymuogens, unite 

 and form-its magnificent Flora, " the most splendid the 

 •world ever saw"-^-Palms, Endogens, are comparatively 

 rare, being' noticed for the first time. Of true Exogens* 

 no trace has been discovered. In the Permian a similar 

 Flora prevailed, though very much reduced in quantity. 

 This system closes the Palasozoic period, Acrogenous 

 plants having predominated Lepidodendron and Sigillaria 

 forming thick beds of coal over large areas towards the 

 close of the period. 



Ascending to the Mcsozoic period, we find in the Trias 

 of this country all organic remains to be exceedingly 

 rare, the plants are few in number, but, throughout the 

 whole period Gymnogens are the prevailing type. Conifers 

 and Cycadaceae are abundant, and give a peculiar character 

 to the vegetation. The Flora of the Oolite differs from 

 that of the Carboniferous system, in the substitution of 

 Gymnogens for Acrogens. In the Cretaceous system, plants 

 are rare, but the former class is fi'eqiient in the green 

 sand. In the Lower Cretaceous dej)osits of Aix-la- 

 Chapelle there are abundant evidences of Angiospermous 

 dicotyledons, or true Exogens; but nothing of this type has 

 been observed in this coimtry. With the close of the 

 system terminates the Mcsozoic period. 



In the Cainozoic or Tertiary period, we find evidences 

 of a very diiferent vegetation, Exogens being decidedly 

 the most abundant, the sub-class Angiospermje far exceed- 

 ing the others. The Endogens, especially the Palms, are 

 numerous, but the Acrogens are comparatively rare. The 

 Flora of the latter part of the period approximates nearer 

 to that of recent times, yet differing much from our 

 present European vegetation. The climate must have 



• Trigonocjrpuni, Cvperacca;, &c. 



