it can be interpreted in relation to that sequence, as a deviation from it due to non-ideal conditions. In these studies, he and Roscoe Pound (who subsequently moved from ecology to legal scholarship) developed the widely-used method of sampling using quadrats around 1898. Clements's climax theory of vegetation dominated plant ecology during the first decades of the twentieth century, though it was criticized significantly by ecologists Henry Gleason and Arthur Tansley early on, and by Robert Whittaker mid-century, and largely fell out of favor. However, significant Clementsian trends in ecology re-emerged towards the end of the twentieth century. Community-unit view of vegetation types or plant communities In his 1916 publication, Plant Succession, and his 1920 Plant Indicators, Clements metaphorically equated units of vegetation, (now called vegetation types or plant communities) with individual organisms. He observed that some groups of species, which he called "formations", were repeatedly associated together. He is frequently said to have believed that some species were dependent on the group, and the group on that species in an obligatory relationship. However, this interpretation has been challenged by the argument that Clements did not assume mutual dependence as an organizing principle of formations or plant communities. Clements observed little overlap in kinds of species from type to type, with many species confined to just a single type. Some plants were widespread over vegetation types, but the areas of geographical overlap (ecotones) was narrow. His view of a community as a distinct unit was challenged in 1926 by Henry Gleason, who viewed vegetation as a continuum, not a unit, with associations being merely coincidental, and that any support by observations or data of clusters of species as predicted by Clements's view was either an artifact of the observer's perception or a result of defective data analysis. Lamarckism Clements was an advocate of neo-Lamarckian evolution. Ecologist Arthur Tansley wrote that because of his support for Lamarckism, Clements "never seemed to give proper weight to the results of modern genetical research." Science historian Ronald C. Tobey has commented that: [Clements] believed that plants and animals could acquire a wide variety and range of characteristics in their struggle to survive and adapt to their environment, and that these features were heritable. In the 1920s, he conducted experiments to transform plant species native to one ecological zone into a species adapted to another, higher, zone. Clements was quite convinced of the validity of