THE DIVISION OF WOBK 23 



ferent kinds of cells, and are called tissues. Every 

 tissue has a special share in the work of the organ 

 in which it occurs. The tendency of protoplasm to 

 divide its work among separate organs is one which 

 allows the living matter to carry on all of its 

 functions most economically and efficiently, and it 

 has been the chief principle in the development and 

 evolution of all living things. 



22. Method of study of functions and organs. — 

 It will be found most convenient to take each organ 

 of the higher plants and learn what we may con- 

 cerning the work it does and the way in which it is 

 done. After a fair conception of the nature of the 

 activities of the plant has been gained in this man- 

 ner, it will be possible to understand much more 

 clearly the mode of life of the simpler organisms in 

 which many kinds of work are carried on by the 

 same tissues or even by the same cell. 



An insight of the special capacities of the separate 

 organs will also enable one to understand the work 

 in which the entire body of a higher plant par- 

 ticipates. 



