Page:Popular Science Monthly Volume 54.djvu/138

128  of the preservation of plants as fossils is explained, the difficulties and sources of error in the determination of fossil plants are pointed out, and the rules for nomenclature and of priority in it are explained. The systematic part follows these introductory chapters, giving as full descriptions as the condition of the fossils admit, with illustrations—one hundred and eleven in all—of those belonging to the orders Thallophyta, Bryophyta, and Pterodophyta, carrying the subject as far as the Sphenophyllales. Technical as the subject necessarily is, the treatment is clear and, where the matter admits, fluent, so that no student need complain of difficulties in that line.



W. Detmer's Practical Plant Physiology is a book of experiments for the use of teachers as well as of students in higher grade schools, and supplies an aid to the study of the whole of that branch of the science by experimental processes. While the arrangement of the material in the second German edition is essentially the same as in the first, nearly every section has been enlarged or remodeled, and the book is essentially a new one; new experiments have been included for lecture demonstration or private work, and pains have been taken to render the book increasingly useful to serious students of plant physiology, especially to those who desire to familiarize themselves with methods of research. Great care has been taken in the selection of research material recommended for the experiments; and material suitable for winter work has received attention as well as summer material. This second German edition is presented by the publishers in the translation in its entirety, without addition or alteration. The two great divisions of the book are into the Physiology of Nutrition and the Physiology of Growth and Movements resulting from Irritability. In the first division the experiments bear upon the food of plants (assimilation, production of proteids, constituents of the ash, and organic compounds as food for plants); the molecular forces and processes (including movements of gases, absorption and movements of water, and absorption of mineral substances in plants); and metabolic processes in the plant. In the second division the characteristics of growing plant structures, the conditions necessary for growth, the influence of internal causes and external conditions; geotropic, heliotropic, and hydrotropic mutations, and other phenomena of irritability; the winding of tendrils and twining plants; dorsicentrality, polarity, and anisotropy and phenomena of correlation; and movements of variation, are presented.

The primary objects of Mr. Hoffman's The Sphere of Science are to point out what constitutes a science, and set forth the ground upon which every science rests and the principles and rules that must be followed in order to construct one. The author maintains throughout that every department of knowledge is capable of scientific treatment, and must be so treated before any great advance can be made toward a consistent and rational conception of the universe. The subjects are considered in succession of the true conception and aims of science, what it takes for granted, the scientific method, certainty and probability in science, the use of the imagination, analogy as an aid, the limitations of science, recent advances in the physical sciences, the old and new psychology, modern scientific ethics, philosophy as the science of the sciences, and the harmony of the sciences. The author holds that the chief need in all departments of thought is not so much mere facts as a new arrangement and classification of facts already at hand; that we can