THE BEGINNINGS OF PLANT LIFE 27 



individual threads, as they rest beside each other, 

 throw out tiny tubes which eventually meet. The 

 cell-walls between them then dissolve, and the 

 contents of one cell pass into the other. This 

 process is shown taking place in our illustration ; 

 and it results in the formation of a spore for a 

 future plant, which by subdivision of its primary 

 cell becomes a thread-like plant like its parents. 



From this stage in plant life a gradual evolution 

 of form and specialisation of cells begins to take 

 place, and in forms slightly higher in the scale 

 certain cells are told off to attach those simple- 

 celled plants to fixed objects, and so we get the 

 first indications of the roots of the higher 

 plants. 



It does not follow, however, when plants 

 are composed of a number of cells, that they 

 necessarily give up the habit of free movement. 

 At Fig. 1 8 is shown an example of one of the 

 most beautiful and interesting examples of pond 

 algae. This little plant is just visible to the eye 

 as a tiny green rolling sphere. When viewed by 

 the microscope, other smaller spherules can be 

 seen within, through its transparent walls. The 

 surface wall of the sphere is covered with a 

 delicate network of protoplasm, dotted with 

 minute green cells, each of which carry two fine 

 threads or " cilia," and it is by means of the rapid 



