xii INTRODUCTION. 



afforded, the pupil begins his study with leaves, the least 

 complex in structure of the organs of plants, and learns 

 to distinguish all their external characters. At the same 

 time he learns the precise terms by which their parts and 

 features are denoted, and these terms become familiar by 

 use in his written descriptions. 



If, in looking over the following pages, objection should 

 be made to so many technical terms, the reply must be 

 that without them it is impossible to gain the mental bene- 

 fits of this method of study. The learning of words is a 

 large part of education, but learned in the usual loose way 

 they favor lax and careless habits of thought. To coun- 

 teract this and give clearness to the mental operations re- 

 quires a discipline adapted to the purpose. Vagueness in 

 the meaning of words necessarily involves vagueness of 

 thought and expression ; while to have clear ideas and be 

 able to clothe them in correct language, it is necessary to 

 know precisely what the words represent. This end can 

 only be secured in the best manner by the objective meth- 

 od, in which the mind is directed first to the observed 

 facts, the specific characters, or the definite relations, so 

 that the terms applied to them acquire fixed and accurate 

 meanings. Careful and minute observations recorded in 

 explicit terms make clearness of thinking and precision of 

 language a habit of the mind. To secure this important 

 object, descriptive botany is superior to any other study. 

 Its terms have been slowly perfected, and are much the 

 same in all languages. The vocabulary of botany is more 

 copious, precise, and well-settled than that of any other 

 natural science, and it is therefore unrivaled in the scope 

 it affords for exercise in clear and accurate thinking, and 

 for the best cultivation of the descriptive powers. 



The method of instruction developed in these pages 

 was devised and carried into most successful practice by 

 the Rev. J. S. Hen slow, Professor of Botany in Cambridge 

 University, England. He had a parish at Hitchin, and 



