522 PREVAILING FAMILIES IN EACH EPOCH. 
are Ferns ; and the greatest part of the remain- 
der are, Cycadese and Coniferae, with a few Lili- 
aceae. More species of Cycadeai occur among 
the fossils of this period, than are found living on 
the present surface of the earth. They form more 
than one third of the total known fossil Flora of 
the Secondary formations ; whilst of our actual 
vegetation, Cycadese are not one two-thousandth 
part. 
The vegetation of the Third period approxi- 
mated closely to that of the existing surface of 
the globe. 
Among living families of plants, Sea weeds, 
Ferns, Lycopodiacea^, Equisetaceae, Cycadese 
and Coniferae, bear the nearest relations to the 
earliest forms of vegetation that have existed upon 
our planet. 
The family which has most universally per- 
vaded every stage of vegetation is that of Coni- 
ferae ; increasing in the number and variety of its 
genera and species, at each successive change in 
the climate and condition of the surface of the 
earth. This family forms about one three-hun- 
dredth part of the total number of existing vege- 
tables. 
Another family which has pervaded all the 
Series of formations, though in small proportions, 
is that of Palms. 
The view we have taken, of the connexions be- 
tween the extinct and living systems of the vege- 
table kingdom, supplies an extensive fund of 
