THE BEGINNINGS OF PLANT LIFE 27 



individual threads, as tliey 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 tixed 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. 18 is shown an example of one of the 

 most beautiful and interesting examples of pond 

 alga?. 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 



