1 



THE PLANT, ITS PARTS AND ORGANIZATION 3 



who have their particular trade or work to perform. In such a 

 community, mechanics, farmers, manufacturers, physicians, 

 lawyers, policemen, merchants, carriers, etc., are groups of indi- 

 viduals who specialize and excel in particular kinds of work. 

 They might be likened to the tissue systems or parts of a plant, 

 all working together for the good of 

 the community. Division of labor is 

 economy for the plant just as it is for 

 a community of mankind. If each 

 individual person performed all the 

 work which was necessary for his 

 existence, civilization would give way 

 to savage life. If each plant cell per- 

 formed all the work which was neces- 

 sary for its existence and perpetua- 

 tion, the present plants which make 

 up our crops, forests and beautiful 

 flowers would give way to a very 

 primitive flora of one-celled plants, or 

 small colonies of cells, while man and 

 the higher animals would disappear 

 from the earth. 



5. The plant cell.-While the cell ^ princi pa f g par 2 ts of the plant: 

 may be regarded as a unit of structure ^Trm?um. stem> leaves and fl wer ' 

 in plants or animals, it has in reality 



a very complex structure. The essential part of a cell is the 

 substance which possesses life, i.e., the living substance. This 

 living substance is protoplasm. It is regarded as fundamentally 

 the same in plants and. animals, although in its finer structure 

 there are some variations in the protoplasm in different organ- 

 isms or in their different stages of growth. 



Plant cells usually have a wall which surrounds the protoplasm 

 and other substances in the cell. The cell wall is secreted, or 

 laid down, by the protoplasm. 



Protoplasm is a slimy, granular substance. In young cells it is 

 often quite dense, with small clear spaces, while in older cells it is 



