DEVELOPMENT AND FUNCTIONS OF CELLS. 

 Fig. 18. 



45 



52. Plants composed of a single row of cells. — In this 

 instance, the cell is multiplied by division combined with sub- 

 sequent expansion which takes place in one direction only. A 

 cell is first elongated, and a partition is seen to project across its 

 middle, by which it is divided into two cells; one of these cells 

 again elongates, and is again subdivided in a similar manner ; 

 in this way, a plant is produced consisting of a simple or branch- 

 ing series of cells placed end to end. Such plants can be seen 

 in any shallow stream of water which is exposed to the light. 

 They appear like threads of vegetable matter, and collectively 

 form that bright-green ooze which attaches itself to the stones 

 and pebbles of the stream. The extension of the parts of 

 plants, or their growth, in all ordinary cases is effected by this 

 mode of cell-multiplication. 



53. In the simplest plant in nature, the plant-cell, both the 

 reproductive and nutritive processes are carried on by the same 



