77 



that it accumulated in the form of extensive and thick beds of peat, 

 which are now coal. Associated with these coal beds near Richmond, 

 and in the Deep and Dan River basins of North Carolina, we have a 

 full representation of the plants from which the carbonaceous matter 

 was derived, and no stronger proof of the wide difference between 

 the floras of the Carboniferous and Triassic ages could be afforded 

 than by the comparison of the plants preserved in the roof shales of 

 the coal beds of Virginia and Pennsylvania; the first being Triassic, 



the second Carboniferous. 



A large number of Triassic plants have also been found at the 

 old copper mines near Abiquin, New Mexico, and at Los Bronces, 

 Sonora, all representing the same botanical groups, cycads in large 

 variety {Otozamites, Podozamifes, etc.), a preponderance of monophyl- 

 lous ferns, with a few of the finer-cut species. 



Of the Jurassic flora of North America very little is known. The 

 Triassic plants are for the most part from the upper members of the 

 series, or Rhaetic beds of the Old World; and it is quite possible that 

 the colored marls and clays which are found about Baltimore, form- 

 ing the summit of the Trias, should be regarded as Jurassic. They 

 have yielded quite a number of plants, principally cycads and finely 



divided ferns, all of new species. 



Cretaceous P/ora.— Nowhere in the world up to the present time has 

 there been found an angiospermous leaf in the Triassic or Jurassic 

 rocks. In India, China, Europe, America, the flora of the Jura and 

 Trias has the character I have already ascribed to it ; but resting 

 immediately upon these beds so full of cycads, conifers and ferns we 

 find in New Jersey, and in innumerable localities in the far West, the 

 Lower Cretaceous sandstones and clays, full of the remains of plants, 

 and these altogether unlike those which had gone before. 



From causes which we cannot as yet understand, nor even conjec- 

 ture, the vegetation of the world was at this period of its history more 

 completely revolutionized than at any previous epoch ; for here came 

 in the angiosperms, by no transition indicated in the record, but by a 

 sudden irruption. At the beginning of the Cretaceous age they seem 

 to have spread over the earth's surface, and soon became the pre- 

 dominant and characteristic forms of vegetation, giving to Nature the 



aspect which she now exhibits. i • • 



Lower Cretaceous clays of New Jersey, and their equiva- 



In the 



West 



Middle Cretaceous strata of the Old World, the remains of at least 

 one hundred distinct species of angiospermous arborescent plants have 

 already been found. With them are many conifers of Araucarian 

 afifinities, and fan palms like those of the present day ; but the forests 

 that covered the continent when the Cretaceous sea invaded it con- 

 sisted mostly of oaks, willows, sassafrases, magnolias, tulip trees, svveet 

 gums— the genera most abundant in our living forests. Here, then, 

 we have according to the present state of our knowledge the be- 

 dnnine of our modern flora. As to where it originated, and by wnat 



