114 



ELEMENTARY BOTANY. 



that the greatest change took place. The Angiosperms for 

 the first time made their appearance, and field. and forest 

 began to assume a somewhat modern aspect. Such genera 

 as the Oaks, Maples, Willows, Sassafras (Fig. 133), Dogwood, 

 Hickory, Beech, Poplar, Liriodendron, Walnut, Sj'camore, 

 Laurel, etc., were each represented by one or more species. 



X 



N- ( 



Fig. 133. 



Fig. 134. 



The groups to which the Angiosperms belonged are as fol- 

 lows : 



(a) Monocotyls. — Graminese, Cyperacese, Liliacese, Naiada- 

 cese, Scitaminese, Dioscoreacese, and Palmacese. 



(6) Dicotyls. — Salicacese, Fagacese, Lauracese, Urticacese, Eri- 

 caceee, Ebenaceffi, Platanacese, Araliacese, Rosacese, Sapotacese 

 and Magnoliaceas. 



6. In the Cenozoio time, which includes the Tertiary and 

 Quaternary periods, the vegetation was decidedly more modern 

 than in the preceding. In the Tertiary period nearly all the 

 genera of the Palms, Grasses, and Dicotyls (Fig. 134) were the 

 same as now, though most of the species are extinct. The 

 Diatoms, too, existed in great abundance ; and immense de- 

 posits consisting wholly of their siliceous shells or valves 

 (frustules), are found in the Tertiary period. The celebrated 

 Bohemian deposit in Europe is fourteen feet thick, and Ehren- 

 berg estimated that every cubic inch of the material contains 

 forty billion shells. The Richmond deposit in Virginia is 



