. The anatomy of woody plants. Botany -- Anatomy. THE LEAF 211 well developed, but are distinctly degenerate in the higher subtribes of the group and are less well developed in any living conifers than they are in Prepinus and Cretaceous species of Finns. The Gnetales often show the transfusion tissues in a high degree of development. The small leaves of Ephedra naturally show them less distinctly than the large persistent foliar organs of Welwitschia, where they constitute a very conspicuous feature of the organiza- tion of the leaf. In Gnetum, again, in accordance with its higher. FIG. 158.—
. The anatomy of woody plants. Botany -- Anatomy. THE LEAF 211 well developed, but are distinctly degenerate in the higher subtribes of the group and are less well developed in any living conifers than they are in Prepinus and Cretaceous species of Finns. The Gnetales often show the transfusion tissues in a high degree of development. The small leaves of Ephedra naturally show them less distinctly than the large persistent foliar organs of Welwitschia, where they constitute a very conspicuous feature of the organiza- tion of the leaf. In Gnetum, again, in accordance with its higher. FIG. 158.—Base of leaf of Casuarina eqitisetifolia, showing transfusion tissue systematic position, the transfusion sheath is less conspicuous. Among the angiosperms transfusion tissues are present in the dicotyledons, but present themselves in the condition typical for the higher gymnosperms only in the genus Casuarina. Here, as is shown in Fig. 157 illustrating the organization of a leafy twig of Casuarina equisetifolia, there are clusters of thick-walled empty cells flanking the leaf traces. This relation to the foliar strands strikingly resembles that found in the higher gymnosperms and appears to be good evidence of the primitive position of this interest- ing genus. In Fig. 158 is shown one of the foliar bundles of the. 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 Jeffrey, Edward C. (Edward Charles), b. 1866. Chicago, Ill. , The University of Chicago Press
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