Energy-diversity theory has gained currency as an explanation for global patterns of species richness. We examine the suggestion of Currie and Paquin (1987; Nature 329: 326-327) that variation in evapotranspiration - a function of moisture availability and temperature that is directly related to plant production - predicts tree species richness in global comparisons. We present contrary evidence: the number of tree species on 26 large (17-7401 kmz) areas of moist temperate forest show continental differences unrelated to geographical patterns in evapotranspiration. Tree species richness of 128 samples of ca 1ha within moist-forest biomes of the world reveal patterns of variation amone continents. and with latitude. that likewise cannot be attributed to eeoeraohi