CHAPTER II 

 THE PLANT AS A WORKING MACHINE 1 



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. 



