CHAPTER VI 



THE PLANT CELL 



General Considerations. — The fact that a plant 

 is an aggregation of small bodies or cells was first 

 brought to general attention in 1667 by Robert Hooke, 

 an English lens manufacturer. This discovery was 

 merely incidental to the attempts then being made 

 to improve the crude lenses of the time; and Robert 

 Hooke used plant sections merely as demonstration 

 objects. Grew and Malpighi, working independently, 

 confirmed Hooke' s observations, and their published 

 researches are the earliest records of work upon the 

 cellular structure of plants and animals. All living 

 bodies are composed of one or more small units or 

 cells. The simplest organisms consist of but one cell 

 (unicellular), all functions necessary to the life and 

 continuance of the species being performed by this 

 individual unit. The more complex organisms begin 

 life as a single cell, but this unit rapidly undergoes 

 division and forms a multicellular individual. In the 

 unicellular organism all life processes are performed 

 by a single cell; but, fairly early in the development of 

 multicellular plants and animals, there occurs a dif- 

 ferentiation of cell structures resulting in the formation 

 of tissues. A tissue is a group of cells of similar 

 structure and is designed to perform a certain work 

 for the organism. The work that a tissue performs 



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