This journal provides immediate access to some articles. Volume 25(2); February 1939 Astronomy Astrophysical Consequences of Metastable Levels in Hydrogen and Helium PMCID: PMC1077713 Botany Growth and Differentiation in Living Plant Meristems PMCID: PMC1077711 Geology and Paleontology The Oxidation-Reduction Potentials of Lake Waters and Their Ecological Significance PMCID: PMC1077717 Mathematics On Ideals of Differential Polynomials PMCID: PMC1077718 Generalizations to Space of the Cauchy and Morera Theorems PMCID: PMC1077719 An Equivalence Theorem for Series of Orthogonal Polynomials PMCID: PMC1077720 Curvature Element Transformations Which Preserve Integrable Fields PMCID: PMC1077721 Physics Expressions for the Current in the Bloch Approximation of “Tight Binding” for Metallic Electrons PMCID: PMC1077716 Physiology and Biochemistry Temperature and the Critical Intensity for Response to Visual Flicker: II PMCID: PMC1077715 Psychology and Anthropology Quantitative Analysis of the Interaction of Individuals PMCID: PMC1077712 The Resolution of Six Tests into Three General Factors PMCID: PMC1077714 Journal Matter Administrative content — journal masthead, notices, indexes, etc. | ||