. The anatomy of woody plants. Botany -- Anatomy. 302 THE ANATOMY OF WOODY PLANTS A condition is paralleled in the reproductive axes of the cones of the living Cycadales and in the seedling of their most primitive genus, Cycas. As regards anatomical organization the foliar traces in their cortical course, and even sometimes in the bases of the petioles, show an interesting resemblance to the bundles of the stem in Medullosa. Fig. 215 illustrates the structure of one of the leaf traces of Cycas re- valuta as it passes through the cortex. The bundle is clearly concentric and consists of a centra
. The anatomy of woody plants. Botany -- Anatomy. 302 THE ANATOMY OF WOODY PLANTS A condition is paralleled in the reproductive axes of the cones of the living Cycadales and in the seedling of their most primitive genus, Cycas. As regards anatomical organization the foliar traces in their cortical course, and even sometimes in the bases of the petioles, show an interesting resemblance to the bundles of the stem in Medullosa. Fig. 215 illustrates the structure of one of the leaf traces of Cycas re- valuta as it passes through the cortex. The bundle is clearly concentric and consists of a central core of primary wood sur- rounded by regu- larly seriate secondary xylem and traversed by wood rays. If the figure under discus- sion be compared with that of a stem bundle of Medul- losa (Fig. 208), it becomes evident that the only striking difference is presented by the much smaller size of the strand of the living genus. The root in the Cycadales presents little that is of interest, since the feature of the presence of centripetal wood is equally exemplified by all roots as a characteristic connected with their extremely conservative organization. It is only between Mesozoic and modern types in which the evolutionary importance of the centripetal wood has passed into the background that the anatom- ical structure of the root comes into the phylogenetic foreground in connection with the doctrine of descent. A feature not of evolutionary interest presented by the cycadean root is the frequent presence of root FIG. 215.—Cortical strand of Cycas revoluta. 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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