CHAPTER II 



FUNDAMENTAL INTERNAL STRUCTURE OF PLANT 



BODY 



Organs and Tissues. — We have said that the seed plant 

 body is composed of a number of members: roots, stems, 

 leaves, and flowers, bearing the fruit and seed. We may say 

 that the plant body is composed of a number of organs, that 

 is, well-defined parts that perform some definite function or 

 functions. For example, those parts of the plant concerned 

 with absorption we call absorptive organs, those that carry on 

 reproduction, reproductive organs, and so on. The roots are 

 the chief absorptive organs of all common seed plants, and 

 the stamens and pistils of the flower the reproductive organs. 

 Now, if we study microscopically the structure of organs, 

 they are'seen to be made up of one or more different groups of 

 cells. Each distinct group of cells within the organ that has 

 a common origin and a common role to perform, is desig- 

 nated a tissue. For example, the pistil (a reproductive organ 

 of a flower) is composed of several different tissues such as 

 parenchyma tissue, conductive tissue, and epidermal tissue. 

 Still deeper analysis of tissues shows all to be made up of 

 small microscopic units — the cells. 



The Plant Cell. — Discovery of the Cell. — The discovery of 

 the plant cell is attributed to Robert Hooke, an English lens 

 manufacturer. In his microscopic study of thin sections of 

 ordinary bottle cork, in 1667, .he observed the cork tissue to 

 be composed of very small compartments, very much aUke 

 in size and shape, and fitting closely together. It happens 



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