188 CIVIC BIOLOGY 



Functional subdivisions, saprophytic, parasitic, and symbiotic 

 fungi. Saprophytic fungi are those that live upon the dead 

 bodies or waste matters of animals or plants. Parasitic fungi 

 attack living animals and plants and injure or kill them. They 

 are the causative agents in the larger part of contagious or 

 infectious animal and plant diseases. Symbiotic fungi live 

 with other organisms, to the advantage of both. Bacteria in 

 root tubercles of the legumes are familiar examples. While 

 convenient, these lines of classification are not hard-and-fast, 

 because it may be difficult, or even impossible, to tell whether 

 an organism, or any part of it, is really dead or alive. The 

 rough bark and the heartwood of a living tree are as dead as 

 they ever will be,- so may be the hair or cuticle of a living 

 animal, or the rind or pulp of a ripe fruit, or the food material 

 of a seed or egg. Who can say whether the sap of a plant or 

 the blood or milk of an animal is dead or alive ? So there are 

 all degrees of liveness or deadness, and a usually beneficent 

 saprophyte may attack a half-dead plant or animal, which we 

 would call alive, but the fungus may know better. Accord- 

 ingly we have Jtemiparasitic and hemisaprophytic, or, so-called, 

 facultative parasitic or saprophytic, fungi that attack the living 

 or the dead according to degrees of vitality or variations of 

 external conditions. 



Botanical position of fungi. All fungi are devoid of chloro- 

 phyll, but not all plants that lack " leaf green " are fungi. 

 Dodder and the Indian pipe are flowering plants that have 

 adopted the parasitic habit, and with this degenerate life they 

 have lost the mechanism and the power of making their own 

 food. So we find from a study of their ways of growth and 

 methods of reproduction that fungi have developed from the 

 algae. Flowering plants reproduce by seeds, which are embryo 

 plants provided with food for the start in life. The ferns, 

 mosses, algse, and fungi reproduce by spores, which, compared 

 with seeds, are almost inconceivably small. Many seeds are 



