. Rapport annuel du Conseil d'administration de la Smithsonian Institution. Smithsonian Institution, Smithsonian Institution. Archives ; découvertes de la science. Les cryptogames, (dicotylédones, } Pheenogams - k, ] les monocotylédones, angiospermes. ( Conifères &AMP ; Cycada^^ Gymnospermes. Les cryptogames vasculaires. Les cryptogames cellulaires. Maintenant, le moyen le plus important de la détermination de la famille des centrales au charbon sont la structure interne de la tige et la nervation des feuilles. Généralement, en effet, ce sont les seuls moyens à oi'ir commande. Ns laisser enquêter, puis, comment les grandes divisions du roi légumes- dom sont ch

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. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. Cryptogams, (Dicotyledons, } k - Pheenogams, ] Monocotyledons, Angiosperms. ( Conifers & Cycada^^ Gymnosperms. Vascular Cryptogams. Cellular Cryptogams. Now, the most important means of determining the families of coal plants are the internal structure of the stem and the venation of the leaves. Generally, indeed, these are the only means at oi'ir command. Let ns inquire, then, how the great divisions of the vegetable king- dom are characterized in these respects. Among Phcenogams there are two very distinct types or plans of internal structure of the stem, viz : the Exogenous, or outside-growing, and the Endogenous, or inside-growing ; the one represented by the hard-wood trees and shrubs, the other by the palms, canes, grasses, &c. On cross section of an exogen (fig. 18) we find three distinct zones of tissue. In the centre a zone of cellular tissue, the pith ; exterior to this a zone of wood, and around this again a zone of cellular tissue, the bark. The zone of wood is, moreover, subdivided into con- centric rings, which represent the annual layers of growth, and sepa- rated into wedges by radiating lines of cellular tissue (silver grain) connecting the cellular tissue of the pith with the cellular tissue of the bark. In the Endogens, on the contrary, we have the woody tissue in the form of thread-like bundles, irregu- larly interspersed amongst the cellular. The dry stalk of an Indian corn is a fa- miliar illustration of this structure. If such a stalk is broken across and the two parts careiuUy separated, the thread-like bundles of woody and vascular tissue are observed to draw Fig. 18. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original

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