CHAPTER V 



CHARACTERISTICS OF THE TRUE FUNGI 



CLASS III. EUMYCETES 



The true fungi or hyphomycetes {v(t)ri, a web + hvktjs, a mushroom) 

 are thallophytes in which the thallus, as the Greek derivation implies, 

 consists of a system of threads {hypha) which form a cobwebby struc- 

 ture known as the mycelium (Fig. 1 1). A single thread of the mycelium 

 is an hypha (plural hyphae) and a hypha may be unicellular, or multi- 

 cellular. All true fungi are colorless, that is they are chlorophylless; 

 and although they may have other pigments present, yet in the absence of 

 chlorophyll, they are dependent plants. 

 As dependent plants, they must get 

 their organic food from extraneous 

 sources, and as all organic matter is 

 either dead, or living, a natural classi- 

 fication of fungi into saprophytes and 

 parasites can be made. A saprophyte 

 {aairpos, rotten + 4>^t6v, a plant) is any 



Fig. II. — Gray mould, Miicoy, . i • i j • •. i • r r j 



showing mycelium and the sporan- Organism which dcrives its chief food 

 gia on upright sporangiophores. supply from dead, or dead and decaying 

 ^^.^^^ ^^ plant organic material, while 

 a parasite {irapaaiTos, one who lives at another's expense) is an 

 organism, which exists at the expense of living animals, or plants 

 (Fig. 12). But some saprophytes may change their mode of nutri- 

 tion and become parasitic; such saprophytes are called facultative 

 parasites, while those which retain their saprophytism under all condi- 

 tions are obligate saprophytes. Again some parasites can adjust their 

 methods of nutrition, so that they can become saprophytes. Such 

 parasites are called facultative saprophytes, while those organisms 

 which are always parasitic are obligate parasites. These distinctions 

 are useful, but it should be emphasized that there is no absolute border- 

 line between one condition and the other. There are imperceptible 



42 



