Origin and Development of Shoots from the Tips of Roots of Pogonia ophioglossoides

Abstract

1. The roots of Pogonia ophioglossoides are horizontal, unbranched, covered with persistent root hairs, and green, at least at their extremities. They are protostelic, radial, triarch to hexarch, with endodermis having conspicuous Casparian strips, and root hairs. They have no root cap. 2. An adventitious shoot begins as a swelling on the root, either at its end or on the upper side a short distance back from the tip. Lateral shoots on roots are more common than terminal ones. The swelling is formed by enlargement and division of the cells of the epidermis and cortex of the root, usually on the upper side, producing a group of meristematic cells which differentiates into a typical bud. 3. The new shoot produces one leaf at each node, and probably one leaf each season, until the shoot is old enough to flower. 4. If the adventitious shoot is lateral, the root may grow forward and produce another shoot the following season. One or two adventitious roots are produced exogenously at most nodes of the adventitious shoot. 5. The formation of exogenous adventitious shoots from tips of roots and of exogenous adventitious roots from shoots is the normal habit of growth in this species of Pogonia, and is apparently of comparatively rare occurrence among plants.