IV PREFACE. 



the book falls naturally into three parts, which may be passed 

 in review as follows: 



Part I. Physiology. Thisdeals with the life processes of plants, 

 as absorption, transpiration, conduction, photosynthesis, nutrition, 

 assimilation, digestion, respiration, growth, and irritabihty. 

 Since protoplasm is fundamental to all the life work of the 

 plant, this subject is dealt with first, and the student is led 

 through the study of, and experimentation with, the simpler as 

 well as some of the higher plants, to a general understanding 

 of protoplasm and the special way in which it enables the plant 

 to carry on its work and to adjust itself to the conditions of its 

 existence. This study also serves the purpose of familiarizing 

 the pupil with some of the lower and unfamihar plants. 



Some teachers will prefer to begin the study with general 

 morphology and classification, thus studying first the represen- 

 tatives of the great groups of plants, and others will prefer to 

 dwell first on the ecological aspects of vegetation. This can 

 be done in the use of this book by beginning with Part II or 

 with Part III. 



But the author beheves that morphology can best be com- 

 prehended after a general study of Kfe processes and functions 

 of the different parts of plants, including in this study some of 

 the lower forms of plant life where some of these processes can 

 more readily be observed. The pupil is then prepared for a 

 more intelligent consideration of general and comparative 

 morphology and relationships. Even more important is a first 

 study of physiology before taking up the subject of ecology. 

 The great \alue to be derived from a study of plants in their 

 relation to environment lies in the ability to interpret the dif- 

 ferent states, conditions, behavior, and associations of the plant, 

 and for this pliysiology is indispensable. It is true that a con- 

 siderable measure of success can be obtained by a good teacher 

 in beginning with cither subject, but the writer beheves that 

 measure of success would be greater if the subjects were taken 

 \i\) in tlic order presented here. 



Part II. Morphology and lije history of representative plants. 



