96 THE CHAIN OF LIFE. 



could find theii way into them. At any time the discovery of 

 an estuarire or lacustrine deposit of Silurian age might wonder- 

 fully extend our knowledge of this ancient flora. 



The Devonian or Erian age, that of the clas^^lc Old R^^d 

 Sandstone of Scotland, is that in wh ch we find the first great 

 and complete land flora ; and though this is inferior in number 

 of species to that of the succeeding Carboniferous, and greatly 

 less important with reference to its practical bearing on our 

 welfare, it is in some respects superior in that variety which 

 depends on diversity of soil and of station. To appreciate 

 this, it will be necessary to glance at the range and subdivisions 

 of the modern flora. 



• In the modern world we divide all vegetation into two great 

 series, that of the Flowering Plants {F/icenogatns), which also 

 produce true fruits and seeds, and that of the Flowerless 

 Plants {Cryptogams)^ which produce minute spores instead of 

 seeds. The latter is in every respect the lower group. This 

 lower series is again divisible into three classes — first and 

 lowest, that of the Seaweeds, Moulds, and Lichens (Thall- 

 ophytes). Secondly, that of the Mosses and their allies 

 (Anophytes). Thirdly, that of the Ferns, Equisetums and 

 Club-mosses (Acrogens). In like manner the second, or 

 higher series is divisible into three classes : that of the Pines 

 and Cycads (Gymnosperms), having naked seeds not covered 

 by true fruits, and woody tissue of simple structure ; that of 

 the Palms and Grasses and their allies (Endogens) ; and last 

 and highest, that of the ordinary timber trees and other plants 

 allied to them, with exogenous stems, netted-veined leaves, and 

 a two-leaved embryo (Exogens). These last are in every 

 respect the dominant plants on our present continents. 

 Carrying with us this twofold division of the vegetable 

 kingdom and its subdivisions, we shall be prepared to under- 

 stand the relation of the more ancient floras to that now 

 living. 



In the Devonian age we meet with no land plants of the two 



