Types of early Flora. 129 
Not only were such quaint forms as the tree rushes or Cala- 
mites, Lepidodendra and Sigillaria present, but the prototype of 
our pine, the Dadoxylon, had made its appearance. 
The same class of flowerless plants known as vascular crypto- 
gams, with the colossal tree ferns added, became more numerous 
and luxuriant in the Carboniferous age, as well as the flowering 
Sigillaria and coniferous Dadoxylon. This vegetation probably 
spread over all the dry land, but the thick deposits of vegetable 
remains accumulating in ne marshy places under dense jungle 
growth and in shallow lakes with floating islands, were finally 
in the course of geologic revolutions, turned into the great coal 
fields. 
In those and subsequent geologic times some of the floral 
types vanished altogether and new ones originated, so that at the 
end of Mesozoic times a considerable change in the landscape 
had taken place. 
In addition to coniferous trees, the palms appeared, and also 
the first of angiosperms, such as the oak, dogwood, beech, poplar, 
willow, sassafras and tulip tree. Species increased in numbers, 
adapted to all sorts of conditions; the forest in a most varied 
and luxuriant form climbed the mountain sides to the very 
crests, and covered the land to the very poles with a flora of 
tropical and semi-tropical species. 
Then came the leveling processes and other changes of post- 
ak ertiary or Quaternary times; the glaciation of lands in north- 
ern latitudes, with the consequent changes of climate, which 
brought about corresponding changes in the ranks of the forest, 
killing out many of the species around the north pole. Only 
the hardier races survived, and these were driven southward in 
a veritable rout. 
When these boreal times subsided in a degree, the advance of 
the forest was as sure as before; but the battle order was some- 
what changed to suit the new conditions of soil and climate. 
Only the hardiest tribes could regain the northernmost posts, 
and these found their former places of occupancy changed by 
fluvial and lacustrine formations and the drifts borne and depos- 
ited by the 1 ice-sheets, while some by their constitution were en- 
tirely unfitted from engaging in a northern campaign or found 
insurmountable barriers in the refrigerated east-west elevations 
of Europe and western Asia. 
In addition, there had come new troubles from volcanic erup- 
