MICRO-ORGANISMS 1 7> 



mately 100 genera. Tlie mycelium in nature may be extensive in de- 

 velopment and may live for years. Many forms are .saprophytic, 

 although a few are parasitic. Like the bracket fungi, many species 

 may be grown in pure culture: some even will produce normal sporo- 

 carps under these conditions. Many forms are eaten, although a fe 

 species are poisonous, especially some members of the genus Amanita. 

 Like the other Basidiomycetes, identification is based on study of the 

 mature fruiting body. The commercial mushroom belongs to this 

 group of fungi. Of considerable importance is the fact that many 

 species develop a vegetative mycelium in association with living plant-, 

 apparently benefiting both the fungus and the plant- 



The last major group of Basidiomycetes, composed of several orders 

 with fewer genera than in the previous groups, is the Gasteromycetes 

 or puff balls. In these fungi large fruiting bodies may occur. The 

 group has, as a common characteristic, basidia enclosed during their 

 development of basidiospores and often permanently so. In puff balls 

 both basidia and basidiospores are formed internally. When the 

 spores are mature and the fruiting body is dry, spores are released by 

 weathering and action of the wind. Approximately 110 genera are 

 known and about 700 species. Most Gasteromycetes appear on the 

 ground, although a few are found on dung or decaying wood. Few 

 Gasteromycetes have been grown in pure culture or studied for either 

 their products or biochemical activity. 



Fungi Imperfecti 



The last major group of true fungi is the "form class' 5 Fungi Im- 

 perfecti, or Deuteromycetes, comprising about 1,350 genera and 11,000 

 species of imperfect fungi; i.e., without a known "perfect" or "sexual" 

 state. Most of these fungi cannot be assigned with certainty to any 

 of the other classes. Included are many important plant and animal 

 pathogens, as well as a great variety of saprobic, or saprophytic, forms 

 generally found decaying vegetation, deteriorating fabric and equip- 

 ment of all kinds, "molding" fruits and vegetables, and inhabiting soil 

 and water. 



The terms "form class" and "form genus" are used when referring 

 to members of this class, because such groupings do not necessarily 

 contain closely related organisms. True relationships are best deter- 

 mined by study and comparison of perfect states and entire life cycles, 

 and in the absence of such information groupings are generally highly 

 artificial. In the case of Phycomycetes and (Jredinales (rusts), how- 

 ever, imperfect states are so characteristic that species can be and are 

 assigned to positions in those groups. The Fungi Imperfecti consists 

 of imperfect forms of Ascomycetes and certain Basidiomycetes. Most 

 of them are undoubtedly conidial states of Ascomycetes. 



Ainsworth (1) stated that of the 11,000 species, possibly a third of 

 them have named perfect states, a third have perfect states not yet 

 named, and the rest have no such states. In any event when the perfect 

 state is known and named and when the connection between the two 

 states is proved, the conidial form is removed from the Fungi Im- 

 perfecti and the imperfect-state name dropped. Where the relation- 

 ship is not definitely proved, or where there is such a difference in the 



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