THE CAEBONIFEROUS AGE. 121 



processes contemporaneously in different parts of 

 either of the great continents. 



But let us consider the actual forms of vegetation 

 presented to us in the Coal period,, as we can restore 

 them from the fragments preserved to us in the 

 beds of sandstone and shale, and as we would have 

 seen them in our imaginary excursion through the 

 Carboniferous forests. To do this we must first 

 glance slightly at the great subdivisions of modern 

 plants, which we may arrange in such a way as to 

 give an easy means for comparison of the aspects 

 of the vegetable kingdom in ancient and modern 

 times. In doing this I shall avail myself of an 

 extract from a previous publication of my own on 

 this subject. 



" The modern flora of the earth admits of a grand 

 twofold division into the Phcenogamous, or flowering 

 and seed-bearing plants, and the Cryptogamous, or 

 flowerless and spore-bearing plants. In the former 

 series, we have, first, those higher plants which start 

 in life with two seed-leaves, and have stems with 

 distinct bark, wood, and pith the Exogens ; secondly, 

 those similar plants which begin life with one seed' 

 leaf only, and have no distinction of bark, wood, 

 and pith, in the stem the Endogens ; and, thirdly, 

 a peculiar group starting with two or several seed- 

 leaves, and having a stem with bark, wood, and pith, 

 but with very imperfect flowers, and wood of much 

 simpler structure than either of the others the 

 Gymnosperms. To the first of these groups or classes 



