All plants are divided into (1) Cryptogams, or Flowerless, such as mosses, ferns, equisetums, and (2) Phanerogams, or Flowering. Flowering plants are again divided into those with naked seeds, as the conifers and cycads (gymnosperms), and those whose seeds are enclosed in vessels, or ovaries (angiosperms). Angiosperms are again divided into the monocotyledons, as the palms, and dicotyledons, which include most European trees. Thus:-- ------------------------------------------------------------------- | (M.A. Brongniart). | |(Lindley). | |CELLULAR | | | | _Cryptogams_ (Flowerless) |Fungi, seaweeds, |Thallogens | | | lichens | | | | | | |VASCULAR | | | | _Cryptogams_ (Flowerless) |Ferns, equisetums, |Acrogens | | | mosses, lycopodiums| | | _Phanerogams_ (Flowering) | | | | Gymnosperms (having |Conifers and |Gymnogens | | naked seeds) | cycads | | | Two or more Cotyledons | | | | Angiosperms (having | | | | enclosed seeds) | | | | Monocotyledons |Palms, lilies, |Endogens | | | grasses | | | Dicotyledons |Most European |Exogens | | | trees and shrubs | | ------------------------------------------------------------------- Adolphe Brongniart termed the coal era the "Age of Acrogens," because, as we shall see, of the great predominance in those times of vascular cryptogamic plants, known in Dr Lindley's nomenclature as "Acrogens." [Illustration: FIG. 10.--_Spenophyllum cuneifolium._ Coal-shale.]