THE BRITTLEWORT FAMILY. 



93 



Fig. 10. 



a. Spore-cases and spores of Algse ; 6. Ditto of Lichens ; 

 c. Ditto of Fungi. 



The Brittlewort Family. 



(DiATOMACEiS.) 



This family consists of microscopical crystalline, brittle, 

 jointed bodies united in straight or curved lines or branched, 

 often separating into pieces and presenting very different 

 forms, being the lowest organisms of the vegetable kingdom. 



The apparent animal motion seen in some of these plants 

 has led to the idea that they belonged to the animal kingdom, 

 but chemical analysis proves them to be vegetable. They 

 appear either in the form of slime on moist earth, stone walls, 

 or in damp, shady places, and even on damp glass, also on 

 stones in fresh water, and on rocks in the sea, often floating 

 and imparting a green, and even a red colour, to the latter, as 

 in parts of the Red Sea, whence its name. Above 450 species 

 have been described and arranged under 45 genera. They 

 exist in all parts of the world, even in the Polar seas, but are 

 not of any special use to man. 



The Conferva iPamily, 



(CONFERVACE^.) 



This family consists of globose, hair, thread, or broad leaf- 

 like bodies, growing on stones and rocks in fresh or salt 



