4 PREFACE. 



course, however short, should include some work of this cha- 

 racter. 



The physiology of plants is given more attention than 

 usual in school text-books, and some representatives of the 

 important classes of vegetable products are included — innova- 

 tions whose importance obviates the necessity of an apology. 



The equipment for the experiments will doubtless be at 

 hand in schools where physics or chemistry is taught. When 

 that is not the case, a mere trifle in the outlay will be suflB- 

 cient. A good pocket lens should be carried by every pupil, 

 for use both in the class-room and in the field. Since each 

 pupil cannot be furnished with a compound microscope, no 

 special directions are given for practical work in histology, 

 though when an instrument is available the teacher should 

 use it constantly in demonstration. 



Most of the figures have been heretofore used in the author's 

 Elements of Botany, where their source is explained. Men- 

 tion should be made that several of the experiments and a 

 few figures have been given essentially as found in Oel's 

 Pflanzenphysiologische Vermche. I have had the assistance of 

 my wife in the preparation of the entire book, and to her, 

 equally with myself, the credit, if any, should be awarded. 



W. A. K. 

 Ohio State University, 1 

 Columbus, Ohio, j 



