6 



PLANT MORPHOLOGY 



much progress was made, that not only were many kinds of primitive 

 land plants in existence, but even such highly developed forms as large 

 lycopods, ferns, and primitive gymnosperms were abundant. 



The Carboniferous was characterized by a wonderful display of plant 

 life. Tree lycopods and horsetails, as well as fern-like and other primi- 

 tive gymnosperms, formed a most luxuriant growth surpassing even the 



densest tropical jungles of today. The accumulated remains of the plants 

 that lived in the vast Carboniferous swamp forests have formed our most 

 extensive coal deposits. 



The plant life of the Mesozoic, except during the Upper Cretaceous, 

 was dominated by the gymnosperms, these being of much more advanced 

 types than had lived during the Paleozoic. Nearly all the large pterido- 

 phytes of the late Paleozoic, as well as the primitive gymnosperms, 

 became extinct early in the Mesozoic. A striking feature of the Creta- 

 ceous was the rise of the angiosperms, as a result of which they came to 

 dominate the vegetation of the entire earth, a position they have main- 

 tained ever since. With the rise of the angiosperms, the gymnosperms 

 have become a subordinate group. 



