CHAPTER II 
THE PLANT AS A WORKING MACHINE? 
5. The parts of the plant. Ordinary plants are composed 
of roots, stems, leaves, flowers, and seeds. Not infrequently 
some of these parts may be absent, or they may be so un- 
usual in form and appearance that their nature is not readily 
seen. Thus, it is not usually evident to others than botanists 
(1) that an onion bulb consists of a very short stem and 
thick, broad leaves, and that when the onion grows, the roots 
descend from the lower part of the stem and green leaves 
and a flower-bearing stem arise from the upper end of the 
stem within the bulb; (2) or that in plants such as turnips 
and carrots the stem and root are not definitely set apart 
from one another; (3) or that the flowers of oak and elm 
trees, so very unlike flowers as we commonly think of them, 
have nevertheless as good a right to the name as has the 
flower of an apple tree. 
The five parts of a common plant together constitute a 
well-organized unit (fig. 3). The parts differ from one an- 
other in structure, in form, and in what they do, but the suc- 
cessful work of each part contributes to the successful work 
of the whole plant. Although we may often be more inter- 
ested in what is being done than in the mechanism which does 
the work, we cannot understand plant work except as we give 
constant attention to the structures of the parts of plants. 
1 This chapter gives an outline of plant structure and plant work. It does 
not present details, but gives a general idea of the nature and functions of 
the plant. If this outline is presented briefly, it serves to interpret the 
more detailed work of later chapters much more profitably than if numerous 
details are presented first. The chapter should be read carefully by every 
member of the class and discussed in one or two recitations, or it may be 
read and discussed by pupils and teacher together. 
6 
