. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. CHAEACTEES AND AEEANGEMENT OF FOSSIL PLANTS. 721 which is often the case, a minute examination of its tissues is the sole method of determining its position in the Natural series. There must also be some general ideas of the vegetation both of the tropics and cooler latittides, of mountain-chains, table-lands, valleys, and estuaries;. Fig 904 Fig. 905. Fig. 906. Fig. 907. more especially of countries characterised by equable, and by excessive or extreme climates, as co
. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. CHAEACTEES AND AEEANGEMENT OF FOSSIL PLANTS. 721 which is often the case, a minute examination of its tissues is the sole method of determining its position in the Natural series. There must also be some general ideas of the vegetation both of the tropics and cooler latittides, of mountain-chains, table-lands, valleys, and estuaries;. Fig 904 Fig. 905. Fig. 906. Fig. 907. more especially of countries characterised by equable, and by excessive or extreme climates, as compared with eontuients, and of humid and desert districts; in short, of all the complex associations with, or dependence of botanical characters upon, surface, soil, and climate, which the globe ; Many of the fossil plants of the tertiary or recent strata may be referred to genera at present existing, and merely present specific dif- ferences ; such as pines, elms, beeches, maples, etc. Those of the secondary strata may, in general, be referred to known families, but in most instances require the formation of new genera; whUe those of the older strata, ia numerous instances, cannot be classed in exist- ing families, and must constitute new groups. From all the iavesti- gations of fossil botanists, however, it appears that the same great types existed in a former state as at the present day, viz. Thallogens, Cellular Cryptogams, Acrogens, Vascular Cryptogams, Monocoty- ledons, and Dicotyledons (including Angiosperms and Gymnosperms). The relative proportion of these classes, however, has been dif- ferent from that of the present day, and the predominance of certain forms has given characters to the vegetation of different epochs. Brongniart gives the following division of fossil plants :— 1. Amphigenous Cryptogamous Plants, Celliilar Cryptogams, or Thallogens, which he subdivides into two classes, Fungi and Algae. Figs. 904-907. Tlie structure of wood in recent C
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