This article reports on a study to investigate the nature of aerial roots in Chinese banyan trees, Ficus microcarpa L.f. and the common belief that their presence and growth is associated with wet atmospheric conditions. First, the form and distribution of free-hanging aerial roots on eight selected Ficus microcarpa trees growing in a public space in Hong Kong, were mapped on their form and distribution. Secondly the extension of selected sample aerial roots from each tree were measured over twelve months against prevailing atmospheric humidity. Lastly, section samples of aerial roots of different ages were taken, and the anatomical structure was observed and compared with that of terrestrial water-absorbing roots to assess the mechanism by which they might take up water. The distribution and growth of aerial roots was observed to be highly variable, but there was a clear link between growth and high levels of atmospheric humidity. The anatomical structure of the aerial roots suggests that while aerial roots could absorb water under certain conditions, their growth was generated from water drawn from terrestrial roots via trunk and branches, and that the association with humid conditions was most likely to be due to the greater availability of ground water in such conditions
