=1. The scope of ecology.= The clue to the field of ecology is found in the Greek word, οἲκος, home. The point of view in the following treatise is constantly that which is inherent in the term itself. Ecology is therefore considered the dominant theme in the study of plants, indeed, as the central and vital part of botany. This statement may at first appear startling, if not unfounded, but mature reflection will show that all the questions of botanical science lead sooner or later to the two ultimate facts: plant and habitat. The essential truth of this has been much obscured by detached methods of study in physiology, morphology, and histology, which are too often treated as independent fields. These have suffered incomplete and unsymmetric development in consequence of extreme specialistic tendencies. Analytic methods have dominated research to the exclusion of synthetic ones, which, in a greatly diversified field, must be final, if botanical knowledge is something to be systematized and not merely catalogued. Physiology in particular has suffered at the hands of detached specialists. Originally conceived as an inquiry into the origin and nature of plants, it has been developed strictly as a study of plant activities. It all but ignores the physical factors that control function, and the organs and tissues that reflect it. =2. Ecology and physiology.= There can be little question in regard to the essential identity of physiology and ecology. This is evident when it is clearly seen that the present difference between the two fields is superficial. Ecology has been largely the descriptive study of vegetation; physiology has concerned itself with function; but, when carefully analyzed, both are seen to rest upon the same foundation. In each, the development is incomplete: ecology has so far been merely superficial, physiology too highly specialized. The one is chaotic and unsystematized, the other too often a minute study of function under abnormal circumstances. The greatest need of the former is the introduction of method and system, of the latter, a broadening of scope and new objectives. The growing recognition of the identity of the two makes it desirable to anticipate their final merging, and to formulate a system that will combine the good in each, and at the same time eliminate superficial and extreme tendencies. In this connection, it becomes necessary to point out to ecologist and physiologist alike that, while they have been working on the confines of the same great field, each must familiarize himself with the work and methods of the other, before his preparation is complete. Both must broaden their horizons, and rearrange their views. The ecologist is sadly in need of the more intimate and exact methods of the physiologist: the latter must take his experiments into the field, and must recognize more fully that function is but the middleman between habitat and plant. It seems probable that