ON THE ANATOMY OF CHENOPODIUM ALBUM L.

Abstract

The Chenopodiaceae and related families exhibit a most striking anomalous structure of the stem in that the annual secondary thickenings contain several circles of collateral vascular bundles of limited development which are embedded in lignified so-called Gheorghieff (I) in a series of publications gives a detailed review of the early literature on this subject. His own contributions, furthermore, comprise the most comprehensive study of the anatomy of the Chenopodiaceae. He finds that the plants which he examined show greatly varied forms, transitional in structure to many of the Centrospermae. Sanio (2) in I863 gives the most complete ontogenetic study of members of the Chenopodiaceae. He attributes the anomalous structure of the stem to the activity of a periodically acting cambium which produces collateral vascular bundles and At the conclusion of his work Sanio draws a comparison between the anomalous stem structure of the Chenopodiaceae and the stem structure of thcse monocotyledons which are characterized by growth in thickness. In his Comparative Anatomy of the Phanerogams and Ferns, De Bary (3) develops a theory to account for the diverse forms of anomalous growth of the vascular tissue of Chenopodiaceae and related families. He makes four general classes. In the plants of the first grcup, an extrafascicular cambium appears around the primary ring of leaf-trace bundles. This cambium remains permanently active and forms alternately on its inner side collateral vascular bundles and conjunctive tissue; on its outer face it forms a thin layer of phloem or none at all. The plants of the second type develop a ring of primary vascular bundles with normal cambium. The activity of the latter soon ceases, and on the outer face of the primary ring appear in centrifugal order a succession of cambia each of which forms a distinct ring of vascular bundles and intermediary tissue. Classes three and four are types intermediate between the first two. Morot (4) points out that the two modes of growth described by De Bary may be reduced to one type. The cambium in each case retains its bipolarity, giving rise to xylem on the inside and phloem on the outside. Fron (5) subsequently states that the stem of Chenopodium album increases in diameter by the activity of a normal and pericyclic cambium, and that this cambium produces to the inside xylem and parenchyma and to the outside phloem tissue.