VII] FUNGI. 207 



VI. FUNGI. 



The most striking difference between the fungi and algae 

 is the absence of chlorophyll in the former, and the consequent 

 inability of fungi to manufacture theii- organic compounds from 

 inorganic material. Fungi live therefore either as parasites 

 or saprophytes, and as the same species may pass part of its life 

 in a living host to occur at another stage of its development as 

 a saprophyte, it is impossible to distinguish definitely between 

 parasitic and saprophytic forms. The vegetative body of a 

 fungus, that is the portion which is concerned with providing 

 nourishment and preparing the plastic food-substance for the 

 reproductive organs, is known as the mycelium. It consists 

 either of a single and branched tubular cell known as a hypha, 

 or of several hyphae or thread-like elements (filamentous fungi). 

 The hyphal filaments may be closely packed together and form a 

 felted mass of compact tissue, which in cross section closely 

 simulates the parenchyma of the higher plants. This pseudo- 

 parenchymatous form of thallus is particularly well illustrated by 

 the so-called sclerotia; these are sharply defined and often 

 tuberous masses of hyphal tissue covered by a firm rind and 

 containing supplies of food in the inner hyphae. They are able 

 to remain in a quiescent state for some time, and to- resist 

 unfavourable conditions until germination and the formation 

 of a new individual take place. The reproductive structures 

 assume various forms; in some of the simpler fungi (Phy- 

 comycetes) sexual organs occur, as in the parallel group of 

 Siphoneae among the algae, but in the higher fungi the 

 reproduction is usually entirely asexual. An interesting case 

 has recently been recorded among the more highly differentiated 

 fungi in which distinct sexuality has been established'. In 

 addition to the reproductive organs, such as oogonia and 

 antheridia, the asexual cells or spores are borne either in special 

 sporangia, or they occur as exposed conidia on supporting hyphae 

 or conidiophores. Thick-walled and resistant resting-spores of 

 various forms are also met with. 



1 Harper (95). 



