Secondary Growth by Means of a Thickening Ring in Certain Monocotyledons

Abstract

1. The structure of the secondary bundles, conjunctive tissue, and secondary cortex of certain monocotyledons is discussed, and the variations or similarities are enumerated. Genera usually may be characterized by the presence of either amphivasal or collateral bundles, and less markedly, by differences in structure of the conjunctive tissue. The elements in both the phloem and xylem and in the secondary cortex are strikingly uniform throughout most of the species examined. The first description of secondary growth in Veratum viride is presented. 2. Growth rings are found in a number of the genera, and depend upon differences in number and position of the secondary bundles, together with variation in wall thickness of the cells in the conjunctive tissue. 3. In the species examined there appears to be no sharp differentiation into areas of distinctly primary or secondary meristematic activity. The cambial initials are of various shapes in tangential view. In the maturation of the secondary bundles, the con...