Making use of paper partition chromatography, an investigation has been made of the nitrogenous compounds that occur free in plants which belong to the Liliaceae or, in some cases, to the Agavaceae or to the Amaryllidaceae. Particular attention was paid to the detection of certain substances which have recently been discovered in plants, namely, azetidine-2-carboiylic acid, γ-methyleneglutamine and certain γ-substituted glutamic acids. Maps record the location on chromato-grams of the identifiable substances from the plants examined and also of the large number of substances that have been observed but not yet identified. The occurrence of these compounds is considered in relation to the taxonomic classification. The natural occurrence of the more unusual soluble nitrogen compounds (γ-methyleneglutamine and other γ-substituted glutamic acids, azetidine-2-carboxylic acid) is taken to indicate the existence in plants of hitherto unrecognized metabolic pathways, and their restricted accumulation may result from changes during the course of selection and breeding in some factor or factors governing these pathways.