PALEOBOTANY BERRY. 395 



ing that time, they furnish some data bearing on the march of 

 vegetation during which flowering plants first appeared in the 

 record and during which the transformation from a Jurassic to an 

 Upper Cretaceous and essentially Cenozoic type occurred. This 

 flora shows evidence in the varying proportions which the main 

 types such as the ferns, Cycadophytes, and Conifers bear to one 

 another, that there are represented plants that grew under local 

 differences of soil, altitude, humidity, and precipitation conditions. 

 It is apparent that the dominant types of the late Jurassic con- 

 tinued without marked change throughout the earlier Cretaceous. 

 These were the ferns, Cycadophytes, and Conifers. Little is known 

 of the Thallophyta, Bryophyta, Arthrophyta, or Lepidophyta. 



The Arthrophyta, represented in the Lower Cretaceous by species 

 of Equisetum had evidently dwindled to proportions strictly com- 

 parable to their present-day deployment. One or two Selaginellites 

 represent the Lepidophytes and several Marchantites represent the 

 Bryophyta. The more characteristic fern families of the older 

 Mesozoic, such as the Marattiaceae, were greatly reduced in im- 

 portance, and the families Schizaeaceae, Gleicheniaceae, Matoniaceae 

 Osmundaceae and Dipteriaceae, which were prominent early in the 

 Lower Cretaceous, were overshadowed by the Polypodiaceae before 

 the close of the Cretaceous, the latter represented by various species 

 of Cladophlebis l and Onychiopsis. ' Pteridosperms were unknown 

 and it is reasonable to suppose that this phylum was no longer repre- 

 sented in the flora of the world. 



Several interesting petrified Osmundaceae are known at this time, 

 and the Gleicheniaceae were especially abundant in the far North 

 along with other ferns indicative of great humidity. A peculiar 

 tree fern represented by petrified fragments of large trunks and 

 referred to the genus Tempskya was very widely distributed in 

 North America and Europe at this time. A typical member of the 

 Schizaeaceae was the genus Schizaeopsis found in the Potomac de- 

 posits of Virginia, with fertile fronds very similar to some of the 

 modern tropical species of Schizaea (fig. 36). A survivor from the 

 older Mesozoic was the Hydropteralean genus Sagenopteris, a hand- 

 some American species of which is shown in figure 37. 



The Cycadophytes of the early Cretaceous were essentially the fa- 

 miliar, even if too little known types of the later Jurassic. They 

 were abundant in genera species and individuals, and were quite as 

 dominant an element of the Lower Cretaceous floras as they had been 

 in the late Triassic and throughout the Jurassic. Before the close 

 of the Lower Cretaceous, however, they became largely extinct. 

 Some of the genera represented in the Lower Cretaceous were Dio- 



1 Some species of Cladophlebis appear to belong to the Osmundaceae. Those from the 

 Potomac appear to represent the Polypodiaceae. 



