Morphology of waterhyacinth plants: A. The "attenuated-petiole" rosette form produced in crowded conditions; B. An expanding axillary bud; C. A developing ramet; and D. The "bulbous-petiole" rosette form produced in open conditions. Abbreviations: ar - adventitious root; bb - bud bract; in - inflorescence; is - leaf isthmus; la - leaf blade; pl - primary leaf; pd - peduncle of flower spike; pt - leaf petiole; rh - rhizome; sp - spathe; st - stolon.