PREFACE. 



Enough work has been outlined in this book for a year's 

 course in those schools that are prepared, by suitable time 

 allotted to the subject and by laboratory equipment, to 

 do comprehensive and thorough work. A term could be 

 devoted to the work outlined in Chapters I to X inclusive ; 

 and where the daily laboratory periods are one hour or 

 less, the entire school year could be profitably occupied 

 by the course there outlined. It is, of course, presumed 

 that the teacher will select from the book such work as 

 the possibilities of his school warrant. It is not expected 

 that each student will perform all of the physiological 

 experiments herein outlined ; but different experiments 

 are to be assigned to individuals or groups of students, 

 the results to be used for purpose of demonstration before 

 the entire class. 



Much stress is laid on laboratory work, which is to be 

 done with the utmost possible care and accuracy, not 

 only that the student may respect his work and that the 

 knowledge gained may be exact, but also that the fine 

 opportunity which the study of plants so richly affords 

 for training in seeing and interpreting facts, may not be 

 passed by. 



In the discussion following each set of laboratory direc- 

 tions it is inevitable that results which the student is 

 expected to work out for himself are sometimes told ; but 



