394 PART IV. VEGETABLE TAXONOMY. 



dons in great abundance and variety. In both of these great 

 groups were also included many modern forms, although the 

 species were nearly all different from those at present existing. 

 Among Monocotyledons were Sedges, Grasses and Palms, and 

 among Dicotyledons, the Beech, Oak, Willow, Poplar, Hickory, 

 Walnut, Chestnut, Birch, Hazel, Alder, Plane-tree, Tulip-tree, 

 Cherry, Buckthorn, Aralia, Sassafras, Laurel, Fig, Persimmon 

 and Sweet-gum. Even such orders as the Leguminosae and Com- 

 postitse, had their representatives. The forests, in fact, had 

 assumed a decidedly modern aspect. 



Of the numerous species of Angiosperms, whose remains are 

 found in the rocks of this period, nearly one-half belong to 

 genera at present in existence ; the rest have perished. Some 

 of the forms most abundant at that time are now represented by 

 only one or two lingering species. There are, for example, 

 but two living species of Liquidamber, the Sweet-gum of our 

 Southern States, and a closely allied species confined to Asia 

 Minor; but one species of Sassafras ; one of the Plane-tree, and 

 one of the Tulip-tree, the last three all confined to the United 

 States, while in the Cretaceous there were several species of each, 

 and these were widely distributed over the northern hemisphere. 



The Coniferous genus, Sequoia, has a similar history. 

 Appearing in the Cretaceous, it nourished through the Tertiary, 

 having its representatives distributed all over the northern hem- 

 isphere, while the present species are but two in number, and 

 these confined to California. One is the Red-wood, Sequoia 

 sempervirens, the other the "Big-tree," S. gigantea. Of this 

 genus at least twenty-six fossil species have been described, and 

 no doubt a much larger number have actually existed. 



