FOSSIL VEGETA15LES. 
4-53 
iHitions of Temperature upon the Land, which 
have been inferred from the remains of the vege- 
tation of the Sea. Thus, in strata of the Transition 
series, we have an association of a few existing 
families of Endogenous Plants,* chiefly Ferns 
and Equisetaceae, Avith extinct families both En- 
fiogenous and Exogenous, Avhich some modern 
botanists have considered to indicate a Climate 
hotter than that of the Tropics of the present day. 
In the Secondary formations, the species of 
these most early families become much less nu- 
merous, and many of their genera, and even of 
the families themselves entirely cease ; and a 
large increase takes place in two families, that 
f^oinprehend many existing forms of vegetables, 
mid are rai*e in the Coal formation, viz. Cycadece 
mid ConiJ'ercB. The unitcdcharacters of the groups 
nssociated in this series, indicate a Climate, 
"diose temperature was nearly similar to that 
"hich prevails ivithin the present Tropics. 
In the Tertiary deposits, the greater number of 
Ihe families of the first series, and many of those 
the second, disappear ; and a more compli- 
^!ited dicotyledonous^ Vegetation takes place of 
* Endogenous Plants are those, the growth of whose stems takes 
P'ace by addition from within. Exogenous are those in which 
growth takes place by addition from without. 
+ Monocotyledonous Plants are those, the embryo of whose 
is made up of one cotyledon or lobe, like the seed of a Lily 
'■** an Onion. Dicotyledonous Plants are those, the embryo of 
