26o OUTLINES OF PLANT LIFE. 



internal chambers in the other. Fungus filaments associate 

 themselves with roots, particularly of trees. Bacteria, in con- 

 nection with roots of the bean family, enable them to acquire 

 nitrogen from the air, as other plants cannot. Fungi and 

 algse, in the relation of master and slave, form the lichens. 

 Algae are similarly enslaved by a few animals. A great 

 number of fungi and bacteria attack other plants and also 

 animals, causing more or less extensive deformity and dis- 

 ease. Only a few seed-plants live as parasites upon others. 



