THE BEGINNINGS OF PLANT LIFE 17 



and larger algae or aquatic weeds. Fig. 8 shows 

 an example of diatom chains in their natural situa- 



Fig 9. An individual diatom-shield (Arachnoidiscus 

 Ehrenbergii) immensely magnified 



tions, clinging to a much larger alga, although the 

 portions shown of this are really microscopic. 

 Others develop foot-stalks, by means of which 

 they attach themselves to stones; &c., and so form 

 little groups or clusters. 



