INTRODUCTION xxi 



lation and storage of water necessary for the plants in the soils 

 of arid regions. Reclamation of lands by drainage of excessively 

 wet soil, as well as irrigation of very dry regions, requires the 

 assistance of plant physiology, which must help to estimate the 

 requirements and peculiarities of the plants for the sake of which 

 expensive improvements are made. 



Plant physiology is also closely connected with plant breeding. 

 The selection and creation of new varieties have the object of 

 increasing the yield and quality of plant products. For system- 

 atically planned plant breeding, it is necessary to be acquainted 

 with the physiological properties of the varieties, their earhness, 

 their winter and drought resistance, etc. Only careful physiolog- 

 ical study of varieties can reveal these properties, and that is 

 why every large institute of plant breeding in Russia possesses 

 at present a physiological laboratory. The chief occupation of 

 such laboratories is the physiological estimating of the more 

 important newly selected varieties and comparison of them with 

 those that have already been accepted as standards. 



In studying microbiological processes in the soil and in investi- 

 gations of agricultural products, agricultural microbiology really 

 represents a special physiology of bacteria and fungi. In college 

 courses of plant physiology, physiological processes related to 

 microorganisms are frequently discussed with no less detail than 

 those pecuhar to the higher green plants. Such a detailed 

 examination of microbiological phenomena, w^hich, by the way, 

 are often more easy to analyze than the processes taking place 

 in the higher green plants, is justified by the fact that many of 

 them throw light on the nature of some of the basic functions 

 of higher plants. Thus the study- of fermentation has aided 

 understanding of the most important process of respiration. In 

 this case, it is difficult to draw a definite boundary between 

 physiology and microbiology. 



Finally, the study of plant physiology leads to the development 

 of new methods of influencing the plant under field conditions 

 with the purpose of increasing the yield and the resistance to 

 unfavorable conditions, accelerating the development of the 

 plant, and improving the quality of its products. Among these 

 methods, mention must be made of yarovisation (vernalization), 

 elaborated by T. D. Lysenko. The method of forcing plants 

 by etherization, warm baths, and different chemical agents was 



