PALEOBOTANICAL EVIDENCE 521 



line between the Jurassic and the overlying Cretaceous; in fact, geologists 

 are not altogether agreed as to just where the separation is to be made. 

 By common consent, however, it is now pretty generally accepted that 

 the line of the Lower Cretaceous shall be drawn at the base of the 

 Wealden, that is, the Neocomian of the European time scale. Plant- 

 bearing beds in this approximate position are abundant and very wide- 

 spread, occurring in England (44 genera, 75 species), Belgium (20 

 genera, 30 species), France (7 genera, 12 species), Switzerland (9 genera, 

 12 species), Portugal (45 genera, 89 species), Germany (33 genera, 50 

 species). Saxony (20 genera, 30 species), South Africa (16 genera, 21 

 species), New Zealand (2 genera, 2 species), Japan (19 genera, 23 

 species), China (4 genera, 6 species), Spitzbergen (18 genera, 32 

 species), and Peru (6 genera, 8 species). Coming to North America we 

 have the Patuxent formation (70 genera, 140 species) of the Potomac 

 group, the Kootenai formation (41 genera, 82 species) of the northern 

 Rocky Mountain region, the upper Knoxville (23 genera, 35 species) 

 beds of California, and beds of approximate age on Queen Charlotte 

 Islands (10 genera, 14 species). 



Berry ^^ has Avritten as follows concerning these early Cretaceous 

 floras : 



"It is apparent that the dominant types of the late Jurassic floras continued 

 without marked change througliout the older Cretaceous. These are the ferns, 

 cycadophytes, and gymnosperms. We know little about the Thallophyta, the 

 Bryophyta, or the Lycopodiales. The Equisetales had evidently dwindled to 

 proportions strictly comparable to their present-day deployment. The more 

 characteristic fern families of the older Mesozoic, such as the Marattiaceoe, 

 are greatly reduced in importance, and the families Schizjieacese, Gleicheniacese, 

 Matoniaceje, Osmundaceje, and Dipteriace?e, which are of great importance in 

 the early part of the Lower Cretaceous, were destined to be overshadowed by 

 the Polypodiaceiie before the close of the Cretaceous. Pteridospermfe are un- 

 known, and it is within reason to suppose that this class was no longer repre- 

 sented in the flora of the world. 



"The Cycadophytes of the early Cretaceous are essentially the familiar 

 types of the late Jurassic. They are abundant in genera, species, and indi- 

 viduals, and are quite as dominant an element in the earlier Cretaceous as in 

 the Rhaetic and Jurassic floras. Before the close of the Cretaceous, however, 

 they became extinct. The other gymnospermic types — the Ginkgoacese, Taxa- 

 cere, and Pinacese — are all represented in the early Cretaceous floras." 



It has been thought by some that the Angiosperm?e, the now dominant 

 modern type of vegetation, was introduced in the low^est Cretaceous 

 (Patuxent) of eastern North America. Fontaine described three forms 



" E. W. Berry: Maryland Geol. Survey, Lo\Aer Cretaceous, 1911, p. 147. 



