XIII 
THE GEOLOGICAL EVIDENCES OF EVOLUTION 
399 
sphere and fixed in the solid state. These great beds of 
graphite, therefore, imply the existence of abundance of 
vegetable life at the very commencement of the era of which 
we have any geological record. 1 
Ferns, as already stated, begin in the Middle Silurian forma¬ 
tion with the Eopteris Morrieri. In the Devonian, we have 7 9 
species, in the Carboniferous 6 2 7, and in the Permian 186 species; 
after which fossil ferns diminish greatly, though they are 
found in every formation ; and the fact that fully 3000 living 
species are known, while the richest portion of the Tertiary in 
fossil plants—the Miocene—has only produced 87 species, will 
serve to indicate the extreme imperfection of the geological 
record. 
The Equisetaceie (horsetails) which also first appear in 
the Silurian and reach their maximum development in the 
Coal formation, are, in all succeeding formations, far less 
numerous than ferns, and only thirty living species are known. 
Lycopodiacese, though still more abundant in the Coal form¬ 
ation, are very rarely found in any succeeding deposit, though 
the living species are tolerably numerous, about 500 having 
been described. As we cannot suppose them to have really 
diminished and then increased again in this extraordinary 
manner, we have another indication of the exceptional nature 
of plant preservation and the extreme and erratic character of 
the imperfection of the record. 
Passing now to the next higher division of plants—the 
gymnosperms—we find Coniferse appearing in the Upper 
Silurian, becoming tolerably abundant in the Devonian, and 
reaching a maximum in the Carboniferous, from which form¬ 
ation more than 300 species are known, equal to the 
number recorded as now living. They occur in all succeeding 
formations, being abundant in the Oolite, and excessively so 
in the Miocene, from which 250 species have been described. 
The allied family of gymnosperms, the Cycadaceae, first appear 
in the Carboniferous era, but very scantily ; are most abundant 
in the Oolite, from which formation 116 species are known, 
and then steadily diminish to the Tertiary, although there are 
seventy-five living species. 
We now come to the true flowering plants, and we first 
1 Sir J. William Dawson’s Geological History of Plants, p. 18. 
