124 Botany 



No. 287. SPOEHR, H. A. The Carbohydrate Economy of Cacti. Octavo, 79 pages, 

 2 text figures. Price $1.00. 



Prerequisite to a rational discussion of the problems concerning the manner 

 in which sugars are formed in the chlorophyllous leaf are a clearer understanding 

 of the conditions governing the equilibria and mutual transformations of the 

 various groups of carbohydrates in the leaf and a more intimate knowledge of 

 plant glycolysis. This paper contains a discussion of some of the reactions which 

 sugars undergo in the presence of various reagents, reactions which simulate those 

 taking place in the living organism and which form the basis of an interpretation 

 of metabolic phenomena. The work consists largely of the analysis of plants 

 (Opuntia versicolor and 0. phceacantha) which had been subjected to various ex- 

 perimental conditions. Special methods of sugar analysis, applicable to this mate- 

 rial, have been worked out and are described. The cacti are characterized by large 

 amounts of mucilaginous material. This is of pentosan nature and comprises a 

 large proportion of the total carbohydrates of the plant. Free pentoses are also 

 present in considerable amounts. The variations of the various groups of carbo- 

 hydrates as effected by the intense seasonal changes to which the cacti are ex- 

 posed are discussed and the results of the special experimental investigations of 

 the factors of temperature and water-content are applied hereto. Results are 

 given of respiration studies under aerobic and anaerobic conditions with special 

 reference to the fate of the carbohydrates and to the conditions of water-balance. 

 The course of consumption of carbohydrates during long periods of starvation 

 and lack of water has been worked out and shows clearly that the pentoses are 

 easily utilized by the plant. Finally the origin and role of the pentose sugars in 

 plants is discussed and a theory of the formation of this group of sugars is form- 

 ulated, based largely upon the discovery of pure glucuronic lactone in the cacti. 



No. 50. LIVINGSTON, BURTON E. The Relation of Desert Plants to Soil Moisture 

 and to Evaporation. Octavo, 78 pp., 16 figs. Published 1906. Price $0.40. 

 Embodying the results of quantitative studies of the moisture conditions in desert 

 soil and desert atmosphere, especially in their relation to absorption and transpira- 

 tion of plants. The conception of relative transpiration is developed and its useful- 

 ness in such studies demonstrated. Some important data on periodic fluctuations in 

 water-loss and exact measurements of the soil-moisture requirements of several 

 species of desert plants are given. 



LIVINGSTON, BURTON E., and LON A. HAWKINS. The 



No. 204. 



Water Relation between Plant and Soil. Octavo, 

 pages 1-48, 3 text figures. 



PULLING, HOWARD E., and BURTON E. LIVINGSTON. The 

 Water Supplying Power of the Soil as Indicated 



Published 

 1915. 

 Price 

 $0.75. 



by Osmometers. Octavo, pages 49-84, 2 text figures. 



The paper by Livingston and Hawkins gives a discussion of the dynamics of the 

 water relation between plant and soil. The results of experiments with three 

 different species of potted plants are presented, these experiments involving the use 

 of the Livingston auto-irrigator as an indicator of soil-moisture conditions and that 

 of the porous cup atmometer for measuring air-moisture conditions. A method for 

 obtaining a quantitative index of environmental aridity (including both air and 

 soil) is here tentatively set forth. 



The paper by Pulling and Livingston presents the results of a study of the re- 

 sistance offered by soils of various water-contents to the absorption of water by 

 osmometers, these instruments simulating the action of the absorbing surfaces of 

 plant roots. Collodion membranes and cane-sugar solution were employed in the 

 osmometers. The paper includes a discussion of the water-supplying power of 

 soils and of the decrease in this power as water is withdrawn. 



No. 284. LIVINGSTON, BURTON E., and FORREST SHREVE. The Distribution of Veg- 

 etation in the United States as related to Climatic Conditions. Octavo. 

 In press. 



The book is the result of a study carried on by the authors during a period 

 of ten years and it presents many new points of view and elaborations of these, 



