40 THE LEWIS BROOKS MUSEUM. 



ance in Europe and America at nearly the same time. The 

 Ohio plants belong to types which are not distinctly defined, 

 and are unlike anything now existing. Some of these are 

 forms which become very abundant in the succeeding De- 

 vonian and Carboniferous ages. They well illustrate the 

 great truth that most of the earliest plants are generalized 

 forms, containing in one individual, characters which be- 

 come later widely separated, distinguishing genera and spe- 

 cies. Their mode of appearance also shows another impor- 

 tant fact, which characterizes the first appearance of the 

 different plants in all geological ages, viz : that new forms 

 arise at first, with but few species and individuals, and often 

 in the era which precedes that in which their greatest de- 

 velopment will be found. 



In the next age, the Devonian, the vegetation has 

 gained in amount, diversity, and grade of organization. 

 The forms which had sparingly appeared in the Silurian, 

 such as annularia, sphenophyllum, ferns, &c, now be- 

 come abundant. Other and higher plants are added. Reed- 

 like plants, the calamites, allied to the scouring rush of the 

 present day, and coniferous trees make their first appearance. 

 The curious compound type of Lepidodendron, allied to the 

 club-moss of the present time, and so characteristic of the 

 lower carboniferous, also occurs for the first time. The 

 vegetation of the Devonian is essentially the same* with that 

 of the next, or Carboniferous age, but is not so abundant, 

 diversified and specialized. In the coniferous trees of the 

 Devonian we have the first indications, from the vegetation, 

 of the existence of high lands. Still, nearly all the vegeta- 

 tion was adapted to growth in low lands and marshes. The 

 presence of tree ferns shows that already the fern family 

 had, in some of its forms, reached its highest point of or- 

 ganization, though as yet but in rare cases. In the Carbon- 

 iferous age the peculiar type ot vegetation which is charac- 

 teristic of the Protozoic time, reached its culmination in 

 yigor of growth and number of species and individuals,. 



