TO THE STUDENT XlX 



purpose that the list of "Questions for Thought and Discussion, " 

 which will be found at the end of each chapter of the following 

 text, has been gathered. The student can tr}^ his hand at these, 

 and if he has first mastered the comparatively few facts presented 

 in the text he should have no great difficulty. The answers to 

 some are easy, almost obvious. Others may be harder to find 

 but will be worth more in the finding. By frequent practice in 

 this sort of exercise he will not only develop and keep sharp his 

 curiosity and his ability to reason and discriminate — the most 

 important ends for him to gain in such a course as this — but he 

 will acquire almost unconsciously a far more thorough under- 

 standing of the structures and functions of plants than he could 

 by merely attempting to memorize a list of facts. The tonic of 

 curiosity and the fresh air of skepticism are sovereign aids for 

 maintaining our minds in that state of health and vigor in which 

 they can steadily assimilate a rich diet of knowledge without 

 becoming sluggish and over-fed. 



