Natural History. 363 



mechanical conception of the forces of life, and the beginning of 

 a return during the last few years to the older theory, which now 

 passes under the name of " neovitalism." w. r. c. 



4. Plant Anatomy from the Standpoint of the Development 

 and Functions of the Tissues, and Handbook of Micro- Technic ; 

 by William Chase Stevens, Professor of Botany in the Univer- 

 sity of Kansas. Pp. xii + 349, with 136 text-figures. Philadelphia, 

 1907 (P. .Blakiston's Son & Co.). — Professor Stevens's text-book 

 is restricted to the anatomy of the Sperinatophytes and consists, 

 as the title implies, of two distinct and independent portions. 

 The first is of more general interest and gives a clear account of 

 the development, structure and arrangement of the various 

 tissues found in stem, leaf and root. Throughout the discussion 

 the functions of the tissues involved are continually kept in mind, 

 and the striking relationships which exist between structure and 

 function are emphasized. Even the more complex topics, such 

 as the differentiation of the stem-tissues from the primordial 

 meristem and the secondary growth in thickness through cambial 

 activity, are fully and adequately treated. The figures are 

 mostly original and include a number of generalized diagrams 

 which ought to be of much assistance to the teacher. The second 

 portion of the book describes the preparation and staining of 

 sections, the use of the microscope, the various reagents and 

 processes used in botanical investigation, the microehemistry of 

 plant products, and the methods employed in the detection of 

 adulterants in foods and drugs. a. w. e. 



5. Der Lichtgenuss der Pfanzen: Photometrische und Physi- 

 ologische Untersuchungen mil besonderer Pucksichtnahme avf 

 Lebensioeise, geographischer Verbreitung und Ktdtur der Pflan- 

 zen / by J. Wiesner, Director of the Institute for Plant Physiol- 

 ogy at the University of Vienna. Pp. viii + 322, with 25 text-fig- 

 ures. Leipzig, 1907 ( W. Engelmann ). — Light has long been 

 recognized as an indispensable factor in certain of the vital phe- 

 nomena of plants, as, for example, in the important function of 

 photosynthesis and in the heliotropic growth-curvatures. With 

 respect to these individual processes the intensity, color and 

 other qualities of light have been carefully investigated. The 

 relationship of the plant as a whole to the intensity of light, 

 however, was a subject which had received but little attention 

 until Professor Wiesner undertook the studies which have resulted 

 in the present work. For this peculiar relationship he employs 

 the term "Lichtgenuss", for which there is no exact English 

 equivalent. It signifies the ratio between the intensity of light 

 which the plant receives and the intensity of the entire daylight. 

 After a discussion of the methods employed in the determination 

 of the intensity of light, the author calls attention to the various 

 component parts of ordinary daylight, distinguishing especially 

 between direct sunlight and diffuse or scattered light. He de- 

 scribes the variations in light intensity to which plants are exposed 

 at different hours of the day, at different seasons of the year and 



