1. INTRODUCTION. 



Tins book has a twofold purpose. First, and especially, 

 it aims to be a guide to a practicable, truly proportioned, 

 logically complete elementary laboratory course in the leading 

 facts and principles of plant physiology. Second, it seeks to 

 provide a handbook of information upon simple physiological 

 experimentation for the use of those who may have any interest 

 in that subject. In both these directions it tries to bring 

 together the best of what is already known, and to add thereto 

 some new suggestions. It is not intended to give physiological 

 information, but to serve as a guide to the acquisition of a 

 general physiological education. 



It is well to note at the outset what place such a course as 

 is here outlined may be expected to hold in botanical educa- 

 tion at the present clay. To those in touch with contemporary 

 botanical progress the answer will be plain. The present 

 movement in the science, both in investigation and in educa- 

 tion, is strongly towards its dynamical phases, --to wards the 

 investigation of the ' * vital ' phenomena of plants (Physiology 

 proper), and towards the elucidation of the factors determining 

 plant structure and distribution (Ecology). This movement 

 is not only manifest in purely scientific study, but is equally 

 plain in economic investigations. It is especially marked in 

 the study of plant diseases (Pathology) in the Experiment 

 Stations, where a knowledge of pure physiology is coming 

 more and more to be recognized as indispensable to successful 

 pathological investigation. Moreover, experience seems to 

 be showing that the physiological groundwork of a general 

 biological education may be obtained best from plants, most 



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