. The anatomy of woody plants. Botany -- Anatomy. 288 THE ANATOMY OF WOODY PLANTS is confined to the outside of the xylem. Endodermal layers, both internal and external, are present, and the pith often contains patches of brown sclerotic cells similar to those found in the cortex. In spite of the fact that the bundles of the central cylinder of the stem are collateral, those of the leaves are concentric in organiza- tion. Applying the principles of comparative anatomy to the situation, we find that in O. cinnamomea the pith and cortex are of common origin and that the bundles of the stele, on
. The anatomy of woody plants. Botany -- Anatomy. 288 THE ANATOMY OF WOODY PLANTS is confined to the outside of the xylem. Endodermal layers, both internal and external, are present, and the pith often contains patches of brown sclerotic cells similar to those found in the cortex. In spite of the fact that the bundles of the central cylinder of the stem are collateral, those of the leaves are concentric in organiza- tion. Applying the principles of comparative anatomy to the situation, we find that in O. cinnamomea the pith and cortex are of common origin and that the bundles of the stele, on the evi- dence furnished by the foliar strands, were formerly con- centric in structure. The conclusion which is reached from the considera- tion of the stem of the species under discussion, in the light of universally valid principles of comparative anat- omy, is that its tubular stele was. FIG. 205.—Part of the stem of O. skidegatensis, still more highly magnified to show the presence of both internal and external phloem. formerly concentric and that the foliar gaps were once large enough to permit of the joining of cortical and medullary tis- sues with one another. The inferences drawn from the data indicated above are, moreover, entirely justified by the considera- tion of the anatomy of the Lower Cretaceous species described in the preceding paragraph. In particularly vigorous specimens of the stem in O. cinnamomea the ancestral condition, moreover, frequently returns, for both open foliar gaps and internal phloem are often seen in such axes. In 0. regalis among living repre- sentatives of the Osmundaceae medullary brown sclerenchyma is occasionally found in the pith, although an internal endo-. 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.
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