THALLOPHYTES 



19 



potatoes are planted, the tuber, composed of vegetative 

 cells, is cut into pieces, and each piece can develop a com- 

 plete new plant. The leaves of some plants can be used in 

 the same way ; grapevines are usually started by planting 

 " cuttings " or " slips " (bits of stem) ; and the process of 

 "grafting" fruit trees really means starting new individuals 



FIG. 14. One of the Red Algae, showing a very much differentiated and complex 



body. 



from vegetative structures. When a new method of repro- 

 duction appears among plants, therefore, it does not mean 

 that the old method is dropped, but that the new one is 

 added. 



A very important fact in reference to vegetable multi- 

 plication remains to be stated. When the cell of a one-celled 

 plant divides, the result is two new individuals; but when 



