28 MINUTE MARVELS OF NATURE 



vibrations of these that the plant rolls itself 

 through the water. 



This little plant is often abundant in ponds, 

 and in reality is a rounded colony of vegetable 



Fig. 17. Thread-like plants, composed of vegetable cells attached 

 to each other (Spirogyra) 



cells ; only a few of which take part in repro- 

 duction. 



Other forms again show indications of the stem_ 

 (see Fig. 19) by producing a row of supporting" 

 cells which take no part in reproduction, this 

 being left to the rows of cells that they support. 

 As our concluding example, a still more advanced 

 type shows a differentiation in the structure of 



