682 FUNGI : GENERAL 



spore-bearing region more or less highly differentiated from 

 the vegetative portion of the plant. 



In the potato-disease fungus, and others of the same class, the 

 sporophore or spore-bearing organ of the plant is a simple or 

 shghtly branched hypha ; but in the mushroom, toadstools, and 

 a large number of fungi it is a complicated and conspicuous 

 structure {A, Fig. 252), and is the only part of the fungus 

 ordinarily noticed, the mycelium from which it springs and upon 

 which it depends being often of slender character, and hidden 

 from view within the substratum on which the plant feeds. 



7. A few species of fungi are monomorphic, that is, they produce 

 but one form of spore ; the majority, however, are pleomorphic, 

 or capable of giving rise to several distinct forms of spores, 

 either at the same time or successively, upon the same 

 mycelium. 



This latter peculiarity has often been the source of confusion, 

 for beforethe life-history had been fully investigated, the several 

 different forms which a species assumed in the course of its 

 development were frequently mistaken for so many isolated and 

 distinct species. 



At the present time thousands of so-called species of fungi are 

 nothing more than incompletely known ' forms.' 



8. Germination of Spores. — With an adequate temperature 

 and a suitable supply of water many spores, especially ordinary 

 endospores and most conidia, germinate in a few hours ; others, 

 such as oospores, zygospores, and many chlamydospores, 

 which are conveniently termed resting-spores, do not commence 

 growth until a certain time has elapsed after their formation by 

 the parent plant. 



In some instances spores require to be in contact with acid 

 or alkaline substrata, or placed under other special conditions, 

 before they will grow. 



The most frequent mode of germination common to most 

 endospores, conidia and oidia consists in the emission of one or 



