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POPULAR SCIENCE MONTHLY. 



cess 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 sys- 

 tematic 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 Pterodojjhyta, 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 liue. 



GENERAL NOTICES. 



Dr. W. Detmer^s Practical Plant Physi- 

 ology * 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 sec- 

 ond German edition is essentially the same 

 as in the first, nearly every section has been 

 enlarged or remodeled, and the book is es- 

 sentially 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 seri- 

 ous 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 ma- 

 terial recommended for the experiments ; 

 and material suitable for winter work has 

 received attention as well as summer mate- 

 rial. This second German edition is presented 

 by the publishers in the translation in its en- 

 tirety, 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 Irri- 

 tability. In the first division the experi- 

 ments bear upon the food of plants (assimi- 

 lation, production of proteids, constituents 

 of the ash, and organic compounds as food 

 for plants) ; the molecular forces and pro- 

 cesses (including movements of gases, ab- 

 sorption and movements of water, and ab- 



* Practical Plant Physiology. An Introduc- 

 tion to Original Research for Students and Teach- 

 ers of Natural Science, Medicine, Agriculture, and 

 Forestry. By Dr. W. Detmer. Translated from 

 the second German edition by S. A. Moor. Lon- 

 don: Swan, Sonnenschein & Co. New York: The 

 Macmillan Company. Pp. 555. Price, $3. 



sorption of mineral substances in plants) ; and 

 metabolic processes in the plant. In the 

 second division the characteristics of grow- 

 ing plant structures, the conditions neces- 

 sary for growth, the influence of internal 

 causes and external conditions ; geotropic, 

 heliotropic, and hydrotropic mutations, and 

 other phenomena of irritability ; the wind- 

 ing of tendrils and twining plants ; dorsi- 

 centrality, polarity, and anisotropy and phe- 

 nomena of correlation ; and movements of 

 variation, are presented. 



The primary objects of Mr. HoffmarCs 

 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 fol- 

 lowed in order to construct one. The author 

 maintains throughout that every department 

 of knowledge is capable of scientific treat- 

 ment, and must be so treated before any 

 great advance can be made toward a con- 

 sistent and rational conception of the uni- 

 verse. The subjects are considered in suc- 

 cession 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, anal- 

 ogy as an aid, the limitations of science, re- 

 cent advances in the physical sciences, the 

 old and new psychology, modern scientific 

 ethics, philosophy as the science of the sci- 

 ences, 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 classifica- 

 tion of facts already at hand ; that we can 



* The Sphere of Science. By Frank Sargent 

 Hoffman, Ph. D. New York: G. P. Putnam's 

 Sons. Pp. 268. Price, $1.50. 



