340 UNITED STATES GEOLOGICAL SUKVEY— TERTIARY FLORA. 



woody texture, and are extremely abundant in the present flora of the whole 

 globe. Therefore its types should, according to the laws of distribution, 

 have been continuous through all the geological epochs. This hypothesis 

 receives a degree of support from the discovery of species of Sclaginella in 

 the Lower Lignitic of Golden and Point of Rocks, and it affords also a 

 confirmation of the supposed relation of the two plants of the Oolite to this 

 family. Anyhow, the Lycopo(liace(X- of our Lignitic flora have such a close 

 analogy to species of Selagindla living in our time, and are so very different 

 from the Lijcopodites of the Oolite, that they positively evidence a far 

 more recent origin. Their facies is Tertiary. Recently, according to Count 

 Saporta, fragments of plants similar to those of our Sclaginella laciniata 

 have been discovered in the Armissan of France. 



The Ferns described from tlie Lower Lignitic measures are all also of 

 Tertiary types. Sphenopteris Lakesii, S. membranacca, S. 7ugricans, and 

 Gymnogramma Gardneri are Eocene according to the same authority, while 

 all the other species represent HymenopliyUum, Ptcris, Woodwardia, Di]jla- 

 zium, Lastrea, Gymnogramma, genera positively Tertiary, rather Lower 

 Miocene, and none of these species have as yet any affinity with the Ferns 

 of the Cretaceous. The predominant type of the Ferns in this last forma- 

 tion is that of the Gleichenice, which appears in the Jurassic, and is in • 

 preponderance in all the series of plants described from the Cretaceous of 

 Europe; Belgium, Moletin; of the Arctic, Greenland, etc.; and also of the 

 Dakota group. None of its species have been recognized in the Lignitic. 

 Thus their absence from its flora indirectly contradicts the reference of this 

 formation to the Cretaceous. 



The genus Salvinia, of which we have three species, is Miocene, at least 

 as far as it is known until now by its five European fossil species. 



The more evident relation of the Lower Lignitic flora to that of the 

 Cretaceous is marked in the Conifers, for of this order we have five species, 

 none of which are identical, perhaps, but positively of types preponderant 

 in the Cretaceous flora. Except one, Ahietites duhius, of uncertain affinity, 

 they all belong to Sequoia, a genus appearing in the Cretaceous and becom- 

 ing predominant in the Tertiary. Its types are extremely persistent, and 

 its species of wide distribution; but, in a fossil state, their specific characters 

 are obscure and difficult to fix. Cretaceous types of Conifers have been 

 found at Point of Rocks, as will be seen below, in connection with more 



