THE ROOT APICAL MERISTEM OF EQUISETUM DIFFUSUM: STRUCTURE AND DEVELOPMENT

The root apical meristem of Equisetum diffusum Don has a prominent four-sided pyramidal apical cell with its base (distal face) in contact with the root cap. Derivatives (merophytes) that contribute to the main body of the root are produced from the three proximal faces of the apical cell. The first division of a proximal merophyte is periclinal to the root surface separating a small inner cell from a larger outer cell. The inner cell is the precursor of the vascular cylinder. The larger outer cell is the precursor of the epidermis, cortex, endodermis, and pericycle. Radial sectors, established early in the development of the cortex, alternate with sectors in the vascular cylinder. These developmental steps show quite clearly that early root development in Equisetum is markedly different from that of most ferns.