CHAPTER I. 
OUTLINES OF THE GENERAL MORPHOLOGY, 
PHYSIOLOGY, AND NATURAL HISTORY OF 
FLOWERING PLANTS AND FERNS. 
The following account is designed as a guide to the 
systematic study of these subjects ; the examples quoted 
are described at greater length in Part II., and the whole is 
arranged for convenience of cross-reference. Further detail 
may be found by advanced students in the various books 
and papers mentioned. The beginner should omit the 
section on general principles, except its first and last 
paragraphs, at his first reading, and return to it when 
he has worked through the other sections on Vegetative 
and Reproductive Organs. 
General Principles. 
Structure and Function. There is reason to believe 
that the great number and variety of plants now existing 
have arisen by a process of evolution or gradual modifica- 
tion from a few simpler forms. The great feature of this 
evolution has been the increasing complexity of the in- 
dividual plant, as ' of the whole vegetable kingdom ; in 
place of simple often almost homogeneous organisms, any 
part of which may perform any function that may be 
required, there now exist also a great many complex 
heterogeneous organisms, with many different parts or 
organs performing different functions, a specialisation which 
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