22 CRETACEOUS AND TERTIARY FLORA. 



the numerous forms of leaves of Liriodendron, so peculiar that they can- 

 not he mistaken for those of any other group or plant; even the Menis- 

 permacecb constitute, by their fossil remains, vegetable groups quite as 

 definite as they could be established from living plants. 



Since the publication of the "Cretaceous Flora" (vol. vi of the U. S. 

 Geological Reports of Dr. F. V. Hayden) the character of the vegetation 

 of the Middle Cretaceous as represented in the Dakota Group has become 

 better defined by the discovery of a large number of specimens of fossil 

 plants, which have increased from 130 to 190 the number of vegetable 

 forms considered specific, already known from this formation. The whole 

 Flora of the Cenomanian epoch, as it is shown in the table of distribu- 

 tion, is composed of 446 species, of which 310 are dicotyledonous and 130 

 are cryptogamous and gymnospermous plants. Of the 190 species of the 

 Dakota Group, 162 are dicotyledonous and only 28 represent crytogamous 

 and gymnospermous plants. 



Numerous works on the Jurassic Flora have sufficiently proven that 

 up to its upper member the Wealden, or lower Neocomian, it is entirely 

 composed of gymnospermous and cryptogamous plants — especially Ferns, 

 Cycadece, and Conifers. The Neocomian, whose vegetation is but little 

 known as yet, shows in its remains the same constituents of its Flora. 

 Upon it is superposed in Germany the upper Neocomian, or Urgonian, 

 from which a series of fossil plants, 22 in number, have been described by 

 Schenk from the Wernsdorf-Schichten of the Carpathian Mountains of 

 Austria; and there also no dicotyledonous plant has been found, and 

 nothing indicates the decadence of the reign of the gymnospermous plants 

 or shows any kind of difference which could lead one to presage the 

 appearance of the Dicotyledons. 



We owe to Heer the most interesting documents on the characters of 

 the vegetation of the Middle Cretaceous — first by the publication of the 

 Flora of Kome, and then of that of Atane, both in Greenland. 



The Flora of Kome, composed of 85 species, has, says the author, its 

 greatest affinity with that of the Wernsdorf shale or upper Neocomian on 

 one side, and with that of the Wealden on the other. With the plants of 

 the higher Cretaceous stages it has only 7 species — Ferns and Conifers — 

 in common. Most of the specimens of the group submitted to Heer's 



