On the Plants of the World before Man. 281 
dron, Vitis, are the predominant plants of the Upper Miocene 
iod. They are most of them, if not all, recognized in the 
present vegetation of North America, to which that of the Mio- 
Guillielme, aud Acer trilobatum, abound, together with species 
described by Heer from the molasse of Switzerland. That pecu- 
Pliocene period is the pPiegecse age of the Huropean flora, the 
time when the climatic conditions are definitively altered, 
when the vegetation becomes gradually poor and ceases to gain 
ture in European conservatories, were until then inhabitants, 
of Kurope, but left it forever. One by one the ostracised plants 
take their departure, lingering here and there on the road to 
