PALEOBOTANY. CHAPTER XLIII. GENERAL RELATIONS OF PLANTS TO TIME. THE subject of Palæobotany or Palæophytology is one which is far too vast to be treated of in a work of this nature; whilst it is one which is of less importance to the general student than that of Palæozoology. For this reason, nothing further will be attempted here than to give the briefest and most elementary outline of the general distribution of plants in past time, to which will be added a short summary of the chief forms of vegetable life which characterise each of the great formations. The following table shows the leading groups into which the Vegetable Kingdom is divided: DIVISIONS OF THE Vegetable Kingdom. I. CRYPTOGAMIC PLANTS (Gr. kruptos, concealed; gamos, marriage), distinguished by having no distinct flowers or fruit. They includea. Thallogens.-Ex. Sea-weeds (Alga), Lichens, Mushrooms. b. Anogens.-Ex. Liverworts, Mosses. c. Acrogens.-Ex. Club-mosses (Lycopodiacea), Ferns, Horse-tails (Equisetacea). II. PHANEROGAMIC PLANTS. (Gr. phaneros, conspicuous; gamos, marriage), distinguished by having distinct flowers and seeds. divided into They are a. Endogens.-Ex. Grasses, Palms, Lilies. These have endogenous stems, showing no rings of growth, and the young plant possesses but a single seed-lobe or 66 cotyledon." Hence they are often called Monocotyledons. b. Exogens.-Ex. Pines and Cycads, with most ordinary shrubs, trees, and flowering plants. The Pines and Cycads, with the fossil Sigillaria, have the seed naked, and are hence called Gymnosperms (Gr. gumnos, naked; sperma, seed). Ordinary trees and shrubs, on the other hand, have the seed covered, and are therefore called Angiosperms. Both the Gymnosperms and Angiosperms have an exogenous mode of growth, with a true bark and annual rings of growth. The seed also possesses two seed-lobes or cotyledons ;" and they are therefore often spoken of as Dicotyledons. 66 The remains of Plants appear for the first time, so far as yet known, in the Lower Cambrian series (the Eophyton of the Fucoi dal Sandstone of Sweden); and from this time onward they are never absent altogether from any of the great geological formations. The affinities of this earliest known plant are so dubious that it cannot be employed as proving the first appearance of any of the great groups of plants. The Upper Cambrian and Lower Silurian Rocks have yielded various remains of an unquestionable vegetable nature, but of doubtful affinities-referred, however, with more or less probability, to Sea-weeds ("Fucoids"). In the Upper Silurian Rocks have been detected various Sea-weeds (Spirophyton, &c.), the spore-cases of Lycopodiaceous plants (Pachytheca), Lepidodendron, and remains of the remarkable generalised type Psilophyton, which is in some respects intermediate between the Lycopodiaceae (Club-mosses) and the Ferns. In the Devonian period-as we now know, from the researches of Dr Dawson of Montreal in particularplants are very abundant, and belong to varied types. The great group of the Gymnospermous Exogens is here represented by remains of various Conifers (Dadoxylon, Ormoxylon, and Prototaxites). The Ferns are represented by numerous species, in many cases not far removed from types now in existence; and it is interesting to notice that Tree-ferns (Psaronius and Caulopteris) are not wanting amongst these. The Lycopodiacea or Club-mosses are represented in the Devonian Series by numerous remarkable types, such as Lepidodendron, Lepidophloios, Cordaites, and Lycopodites. The Sigillarioid plants, regarded by different authorities as being Coniferous, or Lycopodiaceous, or as being intermediate between the Acrogens and Gymnosperms are represented by species of Sigillaria itself, with its Stigmaria roots. The Horse-tails or Equisetacea are represented by species of the remarkable genus Calamites. The genus Antholithes, commonly supposed to be the spike of fructification of some phanerogamic plant, and now known to bear the probably Gymnospermous fruit, Cardiocarpon—is represented by two species in the Devonian Rocks. Lastly, the Devonian formation of the State of New York has yielded the remains of an Angiospermous Exogen, which has been described by Dr Dawson, under the name of Syringoxylon mirabile. We thus see, even from such an imperfect summary as the above, that we must abandon the old view that nothing like a general and varied flora existed in times anterior to the Coalmeasures. We see that at a point of Palæozoic time as early as that represented by the Devonian formation, the earth exhibited a far from scanty vegetation, composed of true land plants, and embracing representatives of almost all the great groups of plants which at present grow upon its surface. Thus, we find in the Devonian Rocks representatives of the groups of the Horse-tails, Club-mosses, Ferns, and Gymnospermous and Angiospermous Exogens. We have, however, no certain representative of the great group of the Endogens, whilst the Angiospermous Exogens are known by a single genus only, represented by a single species. Upon the whole, therefore, the vegetation of the Devonian period is characterised by the predominance of Cryptogams and Gymnospermous Exogens. Passing on to the Carboniferous period, we have to consider the largest and most varied of the Paleozoic floras, but one which is in most respects very similar to that of the Devonian period. Some Devonian genera of plants do not pass up into the over-lying formation, and some of the Carboniferous genera have not been recognised in the Devonian; whilst hardly any species are common to the two floras. Still, the general facies of the Carboniferous vegetation is much the same as that of the Devonian; and the same groups predominate in the former as in the latter, The predominant groups of plants in the Carboniferous Rocks are the Ferns (Filices), the Sigillarioids, the Lepidodendroids, and the Calamites, of which all except the Sigillarioids are certainly Cryptogams. Here, also, we have the first instance of the occurrence of a Fungus (Archagaricon). The Conifera are well represented by several genera (Araucarioxylon, Dadoxylon, &c.), but no remains of trees belonging to the Angiospermous Exogens have been as yet detected. There are, however, a few flowering plants (such as the Monocotyledonous Pothocites of the Scotch Carboniferous). Lastly, the Carboniferous Rocks have yielded remains of the genus Naggerathia, referred by Brongniart to the peculiar Gymnospermous group of the Cycadacea, but regarded by others as belonging to the Ferns. In the Permian period, the vegetation is nearly related to that of the Coal-measures. We have still numerous Ferns (Neuropteris, Pecopteris, Sphenopteris), Tree-ferns (Psaronius), the Lycopodiaceous Lepidodendron, and Calamites. The Conifers, also, are abundant, and belong to several genera. Some of the Conifers, however (as Ullmania), bear genuine cones, and the Sigillarioids, which are so characteristic of the Carboniferous period, have apparently altogether disappeared in the Permian. With the Trias we commence the great series of Mesozoic deposits, and there is a marked change in the vegetation of this period as compared with that of the Carboniferous and Permian epochs. The Lepidodendroids and Sigillarioids have now com |