The present study of life-forms of the Great Smoky Mountains flora is based on the system of Raunkiaer (1934). Realizing the difficulties involved in correlation of meteorological and climatological data with the natural occurrences of plants, Raunkiaer designed his life-form system as a means of defining what he called phytoclimates. The theoretical basis was a familiar one in plant geography (Cain, 1944) and may be expressed as follows: (1) Plants are limited in their capacity to endure different environmental complexes. (2) There is usually a correlation between the morphology (growth-form, life-form) of an organism and its environment, i.e., there is a morphological basis for adaptation in many if not all cases. (3) A plant, in its successful existence, represents what may be called an automatic physiological integration of all the factors of its environment. It follows, if these are general truths, that the life-forms of the plants of an area are a measure of the environmental conditions, especially climate. It remains only to find the key to the plant-climate interrelations.