72 



ACADEMIC BOTANY. 



their young in a pouch (like the Opossum), come in. At the close of 

 the Jurassic period the Sierra Nevada, Wahsatch, and Humboldt 

 Mountains were thrust up in North America. Europe was still an 

 archipelago ; eastern and southeastern England was still submerged. 



134. In the Cretaceous period Diatoms and Desmids abound. Palms 

 increase. Exoqbns appear, — fossil leaves of the Oak, Poplar, Beech, 

 Willow, Dogwood, Sassafras, and Tulip-tree. Huge reptiles continue; 

 Middle Time is called the Age of Reptiles. The birds resemble Cor- 

 morants and Waders ; but their teeth are pointed, like a' reptile's. 



The climate of the world was still mild. At the close of this period 

 disturbances occurred, and life was again exterminated. The Rocky 

 Mountain region arose above the seas and became a level plateau. But 

 the Gulf of Mexico still extended to the mouth of the Ohio Kiver, and 

 covered the whole area east of the Kocky Mountain plateau as far as 

 the Arctic Circle, 



135. Modern Time has two periods : 



1. Tertiary, or Third, so called because Lifeless Time was once 

 called Primary, Ancient and Middle Time Secondary ; 



2. Quaternary, or Fourth, sometimes called Kecent. 



136. In the Tertiary Diatoms still abound. Perns and Pines sink to 

 their present proportions. Exogens appear very nearly as they are to- 

 day. The Butterfly and Bee 

 come in with the flowers ; we 

 see them embalmed in Amber 

 (Fig. 86), which is the fossil 

 resin of some coniferous tree. 

 The strange animals disap- 

 pear; the higher Mammals 

 come In, — the Whale, Horse, 

 Hog, Elephant, Ox ; the Ter- 

 tiary is the Age of Mammals. 

 The Pheasant and Wood- 

 peckej, the Wildcat and Deer, 

 appear in the woods. The 

 Monkey is their comrade, and 

 grins at us with an ancestral 

 familiarity that cuts down 



our self-conceit. The earth still preserved a mean temperature of 48° 

 Fahrenheit. At the close of this period there was another upheaval. 

 The Pyrenees, Alps, and Carpathian Mountains were made in Europe; 

 the Himalayas in Asia ; the Eocky Mountain plateau was thrust up 

 into its present line of mountains. But the Gulf of Mexico still ex- 

 tended to the mouth of the Ohio Kiver ; Florida and the Atlantic States 

 were submerged as far as New York. 



137. The Quaternary is the Age of Man. It has three periods : 



1. Glacial, in which moving glaciers in high latitudes modified the 

 surfaces of continents ; 



2. Cham.plain, in which the ice passed away and coast deposits were 

 formed ; 



3. Recent, or Terrace, in which the land was raised approximately 

 to its present level. 



138. In the Glacial and Champlain periods Man is first seen as a 



Fia. 86. — Amber, with remains of fossil insects. 



