If there were no vegetation, the rate of evaporation from land surfaces after rain would diminish rapidly to a very low value. Plants increase this rate by transpiration. In this process, water is transferred from the soil through the roots to the leaves by osmosis and capillary action. Water evaporates from the surface of the leaves and the resulting vapour diffuses into the atmosphere. For hydrological measurements, this phenomenon is frequently lumped with evaporation because the two processes are not truly distinguishable using simple observational techniques over an area of mixed land use. The complete process of removal of moisture to the atmosphere from land surfaces by evaporation and transpiration is then termed evapotranspiration.