CHAPTER X 

 SAPROPHYTIC FUNGI 



MUCOR AND PENICILLIUM. 



THE Fungi differ from the Bacteria in being plants 

 whose bodies are composed, not of single cells and 

 cell colonies, but of delicate branching threads which 

 grow in liquid or solid " substrata " containing organic 

 substances which they can absorb as food, and often 

 sending branches into the air. This system of branch- 

 ing threads is called the mycelium, and the individual 

 branches are called hyphce. The mycelium of many 

 species is large and conspicuous. As a general rule 

 fungi can only grow actively in damp situations, and 

 they are commonest when and where the air contains 

 a large amount of water vapour. 



Fungi may be either saprophytic or parasitic (see 

 p. 78), i.e. they may either take their food exclusively 

 from the tissues of a living organism (plant or animal) 

 or they may take it exclusively from a non-living 

 organic substance, e.g. the dead bodies of organisms, 

 dung, milk, cheese, jam, leather, etc., or from humus 

 (seep. 154). But this distinction is not absolute. For 

 instance a parasitic fungus may begin its life in the 

 living body of an animal or plant and continue to 

 grow after the " host " is dead. Or a fungus which 

 is ordinarily a saprophyte may, on occasion, attack 



