D INTRODUCTION. 



they know any thing of the subject or not, and by pupils with- 

 out any assistance at all. A large amount of time will not be 

 required, but the exercises should be so frequent and regular 

 as to keep the subject prominently in mind, and maintain the 

 interest in vegetable forms. 



The Second Book begins where the First left off. The use 

 of magnifying-glasses and microscopes is commenced, and the 

 work now becomes more close and thorough. As soon as the 

 more important features of the flower are known, the pupil 

 is introduced to the leading principles by which plants are 

 arranged, and set to making groups of those that most nearly 

 resemble each other in important characters. He is here called 

 upon to do his own thinking, and to form opinions as to the 

 amount of resemblance between different plants. He has to 

 decide whether a certain group of characters presented by his 

 specimen is most like one or another group presented by 

 other plants, and this leads on to the comparison and estimate 

 of the relations of different groups with each other. It is thus 

 that the discipline of the judgment and reason begins to be 

 secured at an early stage of the study, and is continued with 

 more and more completeness as it goes on. 



I am much indebted to the kindness of Mr. George C. 

 Woolson for having carefully revised the proofs of the present 

 volume, and have also to thank Prof. George Thurber for valu- 

 able suggestions, both in regard to the present work and the 

 revised edition of Prof. Henslow's Charts. 



E. A. T. 

 NEW YOKK, June, 1873. 



