534 F. H. KXOWLTOX EVOLUTION OF GEOLOGIC CLIMATES 



Saporta makes elaborate comparisons of the Aix flora with that now 

 living in various parts of the world, notably Asia and Africa, and con- 

 cludes that the climate was tropical or subtropical. 



Other large floras of about the same age as the last are known from 

 Haring, in the Tyrol, and several localities in Dalmatia; but they need 

 not be further considered here. 



Miocene floras and their climatic requirements. — The known Miocene 

 floras of Xorth America are relatively unimportant, although in the ag- 

 gregate probably somewhat over 500 species have been indicated. The 

 deposits occur in often small isolated basins that in some cases are sepa- 

 rated by hundreds of miles. Thus, the only flora of any importance in 

 the entire area east of the Eocky Mountains is at Brandon, Vermont, 

 where there are small pocket-like deposits of lignite in the midst of 

 ancient crystalline rocks. These have yielded large numbers of fruits 

 and seeds and a very few poorly preserved leaves. Upward of 150 

 nominal species have been described, many of which are referred to form 

 genera, such as Bicarpellites, Cucumites, Tricarpellites, Brandonia, 

 etcetera, with a few suggesting affinity to modern genera, as Xyssites, 

 Hicoria, Juglandites, etcetera. There is so much uncertainty regarding 

 the botanical allocation of these forms that it is impossible to draw very 

 satisfactory or convincing conclusions as to the climatic conditions under 

 which they grew, though obviously they must have been quite different 

 from present conditions. However, as certain of the lignites studied 

 show well marked growth rings, it is apparent that there must have been 

 well defined seasonal changes of some sort. 



At Florissant, Colorado, also in the midst of older crystalline rocks, 

 there are small lake-bed deposits which have afforded vast quantities of 

 plant and insect material that is largely in an admirable state of preserva- 

 tion. About 1,000 species of insects and upward of 200 species of plants 

 have been described. According to Scudder, the insects show certain 

 tropical affinities, but also embrace representatives of forms now living 

 in the vicinity. Much the same can be said of the plants; for, though 

 the general facies of the flora is abundantly different, there are a number 

 of generic types that are now living in the region. Certain important 

 types show relationship with the flora of the Southern States and the 

 West Indies and indicate that the climate was considerably warmer than 

 the present one. Large silicified trunks of Sequoia are found in these 

 beds, and, as they show well defined growth rings, it is an indication 

 that there were marked seasonal changes of temperature. It is also 

 evident that there was a greater degree of moisture, and altogether it 



