Abstract:A newly recorded species of China, Myriophyllum siamense (Craib) Tardieu (Haloragidaceae) found in Hainan Island, China was reported and described. The species is semi-aquatic, without pinnate leaves and with highly reduced male flowers. In terms of morphological characteristics, it is related to some species in Australia and Oceania, and provides evidence for the intercontinental spread of Myriophyllum. Its discovery also shows that there are still many weak areas and blind spots in Hainan Island.
