Anatomy of Seedling Buds of Quercus

Abstract

1. The primary stem of Quercus alba and Q. rubra shows two distinct initial groups, one for the dermatogen and a second (subterminal) common to both periblem and plerome. Distinct cauline strands may be distinguished in the primary tissues of the epicotyl only at an early stage of seedling development; such strands apparently taking their origin just beneath the initial regions and from the marginal cells of the plerome. 2. With the appearance of leaves or leaflike appendages at the stem tip, the vascular elements of these members (the foliar strands) become the dominant bundles of the primary cylinder. This fact no doubt has led to the commonly accepted idea that the primary cylinder of the more ancient dicotyledons consists only of bundles of the leaf trace. 3. The tissues of the leaf appear to originate from two initials: one for the epidermis, the second for the parenchyma and the bundles. 4. The procambial strands of the foliar organs originate in the bases of the leaf primordia. Differentiation of these strands progresses from the point of origin both basipetally and acropetally. The first thickening of xylem elements occurs in the procambial tissue in this region. 5. Both species of Quercus examined furnish evidence of variable nodal structure, the character of the node being largely determined by the nature of the developing foliar organs.