241 



can Permiau, mostly represented by magnesiau limestone, has till now 

 contributed to paleontology but a few specimens of Calamites only. In 

 Europe, tlie flora of this period, known especially by an admirable work 

 of Goppert, is composed of Ferns and Uquisetacece, with very few Lyco- 

 podiacece and many Conifers of peculiar type, — the Volsia, ValcMa^ Jill- 

 niannia, etc. ; types limited to this formation, without known precursors, 

 and with few successors. It has, however, a dozen species of Conifers, 

 known by the texture of the fossilized trunks, and referable to that 

 genus Araucaroxylon to which belong the fossil trunks of our Devonian. 



We have seen that some species of the Carboniferous ferns ascend in 

 Europe to the Permian. Even the American species of some localities 

 (some of those, for example, represented in the concretions of Mazon 

 Creek, Illinois) have a facies which appears to Schimper so evidently 

 Permian, that he is disposed to refer them to this formation. These 

 concretions, hoAvever, like the coal-strata with which they are connected, 

 are in our Lower Carboniferous. They overlay at Morris the Subcarbon- 

 iferous limestone, and at Colchester are separated from the Millstone 

 Grit by only a few feet of strata, and, besides the connection of these 

 plants in the same strata with remains of Lepidodendron and their 

 fruits, large species of Alethopteris, etc., is sufhcient evidence of their 

 age. 



The flora of the Trias is not distinctly represented in the North Amer- 

 ican geology ; for the deposits of coal near Eichuiond, Va., and in 

 North Carolina, referred to this period, are, from the character of the 

 fossil plants, rather related to the lowest member of the great Jurassic 

 period — the Triasso-Jurassic or Ehetic of the European geologists. 

 These plants represent a few species of Equisetum and a large number 

 of Ferns, wherein the genera Pecopteris and Sphenopteris are scantily 

 represented. One of the most remarkable types is that of Clathro- 

 pteris, a fern with large runcinate leaves, whose form and areolation in 

 broad square areas bear some likeness to leaves of dicotyledonous 

 plants. The essential components of the coal, however, as indicated by 

 the fossil remains, are Cycadce, — Fodozamites, Pterophyllum especially, 

 and Conifers of a peculiar group of the Firs. This fossil flora is not sat- 

 isfactorily known ; its characters appear intermediate to those of the 

 Triassic, where begins the reign of the Gymnosperms, which contin- 

 ued on through the whole Jurassic period. 



These are the dark ages of the vegetable world. In the North Amer- 

 ican continent, not a single plant is known as yet from the Jurassic, 

 which, in its subdivisions — Lias, Oolith, Corallien, and Wealden — is 

 represented in some parts of Europe by many thousands of feet of meas- 

 ures. Even in Europe, the vegetation of this period is comparatively 

 little known. Scarcely five hundred species of plants have been as yet 

 recognized from the whole of its divisions. Of these, sixteen per cent, 

 are referable to Algce, or marine plants; four to Equisetacece ; forty-one 

 to Ferns; and forty-five per cent, to Gymnosperms ; of these, twenty-nine 

 per cent, are Cycadce^ and the balance, twelve per cent., Conifers. A few 

 monocotyledons of uncertain relations, mostly Tuccacites, with two spe- 

 cies of Chara, are described from the upper stages of this formation. Of 

 course, we do not know what riches of vegetable remains this long period 

 may keep in reserve for the study of future paleontologists. It is, how- 

 ever, fair to presume that the essential characters of its flora are known 

 already, and that, indeed, it is essentially composed, for the land vegeta- 

 tion, of Acrogens, and especially of Gymnosperms. Till the Cretaceous 

 period, no traces of dicotyledonous plants have been recognized. 



This brings us to the examination of a number of fossil plants recently 



