Regeneration of Podostemon ceratophyllum

Abstract

1. Podostemon ceratophyllum has an unusual capacity for regeneration, which is possessed by each of its vegetative organs, and this regeneration can readily be observed in laboratory cultures. 2. If the distal end of a root is cut off, a new root growing point is initiated back of the cut surface. The root cap is formed from the tissue between the meristem of the root growing point and the cut surface. 3. Occasionally cases of heteromorphism occur in root cuttings. 4. In contrast to known cases of regeneration of root tips in other forms, a new root growing point may be formed in Podostemon ceratophyllum regardless of how much of the distal end of the original root is cut off. 5. A root is also initiated at the proximal cut end of a stem, and it continues the axis of the latter. Its dorsal and ventral sides correspond to those of the stem. 6. A shoot is regenerated at the distal cut end of a stem. The first two leaves of the regenerated shoot arise from dedifferentiated cells within the stem bundle a short distance back of the cut surface. The regenerated shoot continues the axis and the dorsiventral symmetry of the original stem. 7. A detached leaf regenerates a root at its proximal end; the distal end of the petiole regenerates a shoot. In both cases the regenerated organ continues in line with the axis of the original organ. 8. When two or four roots are regenerated at the same cut end of a root, these may be laterally concrescent for 1 mm. to 10 cm. or more. Two shoot axes also may arise simultaneously at the distal end of a stem fragment. These are not concrescent.