All kinds of resistance model of evaporation, from the simple single-layer to complicated multilayer-models, have been widely applied. There is an argument in literature that single-layer models are incorrect but useful, whereas multilayer models are correct but useless. Discussion and judgement on these two kinds of model were made in this paper, both models have sound physical basis, but they are best suited for somewhat different tasks. Both types of model are therefore correct and useful within their respective sphere of approximation and applicability. Single-1 yer models are appropriate where one is concerned with vegetation essentially as a permeable lower boundary to the atmosphere (or upper boundary to the soil) in system with a length scale much larger than that of the vegetation itself; for example, in studies of the atmospheric planetary boundary layer and the atmospheric general circulation, or in hydrological modelling of medium-scale or large-scale catchments. On the other hand, multilayer models are appropriate when it is necessary to resolve detail within the canopy, either because the detail is important in its own right or because the height scale of the vegetation is comparable to that of the system under study, for example, the interaction between microclimate and physiology, or the hydrology of small forested catchments.