216 BOOKS AND CURRENT LITERATURE 



directly the root growth of Frosopis velutina and Opuntia versicolor and 

 found that these plants responded in a different manner to various 

 mixtures of carbon dioxide and oxygen. Livingston and Free^ observed 

 marked differences in the rate of water absorption by roots of willow 

 (Salix nigra) and coleus (Coleus hlumei) when the soil atmosphere of these 

 plants was deprived of oxygen by replacing it with nitrogen. The wil- 

 low showed no signs of injury when oxygen was excluded from its roots 

 while the coleus showed an almost complete cessation of water intake 

 within a few hours. The root system of the coleus grown with deficient 

 oxygen was poorly developed. Neriiim oleander and Heliotr opium peruv- 

 ianum were also found to show injury when their root systems were 

 deprived of oxygen. 



It is indicated by these various experiments that injury is due to 

 lack of oxygen necessary in the process of respiration of the root cells. 

 The apparent exception of normal growth in Salix when deprived of 

 oxygen raises the question as to whether the respiration of the roots 

 of that plant and other similar ones might not be anaerobic. ^Earl 

 S. Johnston. 



A Text-Book of Botany. — Still another text-book giving elements 

 of botany!^ There is, apparently, no common opinion, nowadays, as 

 to what constitutes the elements of botany. Instead, one finds almost 

 every teacher, called upon to give a course to persons beginning to 

 study botany, compounding this course of certain well-known ingredi- 

 ents, of certain subjects "which every boy should know," and of certain 

 other topics upon the indispensable merit of which no two other teach- 

 ers agree. The product commonly includes some vestiges of the Gray- 

 ian "morphology," a modicvun of the Sachs-Bessey-Farlow-Campbell 

 "type" scheme, with more or less emphasis of the idea that these "types" 

 may give a plausible indication of the course of evolution of plants, 

 some cytology and some bacteriology perhaps of the Strasburger and 

 Cohn kinds, some physiology, some pathology, some plant breeding, 

 and, especially since the smnmer of 1914, some economic botany. This 

 inclusion of so many topics in one general course leads in practice to 

 the theoretic results — confusion and dissipated interest. And what con- 



3 Livingston, B. E., and Free, E. E., The effect of deficient soil oxygen on the 

 roots of higher plants. Johns Hopkins Univ. Cir. n. s. no. 3. 1917: 182-185. 

 1917. 



1 Allen. Charles E., and Gilbert, Edward M. Text-book of Botany. Boston, 

 D. C. Heath and Company, 1918. 



