Soil moisture in relation to plant growth is expressed upon the basis of its availability to the plant. Botanical or agricultural papers in which comparisons are made of the effects of different soils and soil moistures upon the growth of plants must necessarily consider the ability of the plant to obtain the moisture present in the particular soil. It is apparent however to those who have given such problems some study that our methods of determining the availability of water in a given soil are not very accurate nor very easily applied. It was with the view in mind of studying the plant in wilting and to improve, if possible, some of the methods used in investigating the water relations at wilting that this work was undertaken.