10 MISCELLANEOUS PUBLICATION 95 5, U.S. DEPT. OF AGRICULTURE 



time of development or substrate conditions that often only the conidial 

 state is present, it is desirable from a practical standpoint to retain the 

 conidial-state name among the Fungi Imperfecti, because in identify- 

 ing the organism it would be sought there. Thus we sometimes find 

 two names referring to the same organism. The gibberellin producer, 

 for example, although preferably called by its perfect-state name, 

 Gibberella fujikuroi (Saw.) Wr., is sometimes called Fusarium monili- 

 forme Sheldon when only the conidial state is present. 



The morphology of the imperfect f ungi^ varies a good deal and is 

 generally used as the basis for classification. Mycelial hyphae are 

 septate and similar to those of the Ascomycetes and Basidiomycetes. 

 Except for a few that form no spores, the various species develop one 

 or more types of conidia, which are commonly borne on special mycelial 

 branches of varying complexity. These special branches, or conidio- 

 phores, may arise singly or in clusters, variously termed "coremia," 

 "synnemata," and "fascicles." Some species form their conidia in or on 

 special fruiting structures termed "pycnidia," "acervuli," and "sporo- 

 dochia." These special structures may or may not be produced in 

 culture, and identification of species sometimes depends on their 

 presence. 



Conidia are many. They may be almost any color, shape, or size. 

 Some are produced singly; others are arranged in chains, heads, or 

 mucoid droplets. Some are pinched off the ends of conidiophores ; 

 others are formed in or at the tips of special flasklike hyphal tips 

 called phialids. They may be warted, spiny, or even have various kinds 

 of appendages. Some are single-celled; others can be two-celled or 

 even many-celled, with the cells arranged in various characteristic 

 patterns, which aid in identifying genera and species. 



The imperfect fungi are usually classified in the following orders : 

 Sphaeropsidales, which contains the four families forming pycnidia ; 

 Melanconiales, which has the single family forming acervuli; Moni- 

 liales, which includes the remaining six families forming conidia ; and 

 Mycelia Sterilia, which has the few genera not producing conidia. 

 Most of the so-called common molds are located in the Moniliales, which 

 contains the two families of imperfect yeasts, in addition to such 

 familiar genera as Aspergillus. Penicillium, Alternaria, Cladosporium, 

 and Fusarium. 



Almost all the common imperfect fungi can be cultivated readily on 

 agar media. Some that produce great numbers of spores are often 

 even laboratory pests, contaminating sterile agar or cultures of other 

 organisms. Members of the Sphaeropsidales and Melanconiales gen- 

 erally sporulate less readily than many of the Moniliales in artificial 

 culture, occur less commonly as soil forms, and therefore are present 

 in fewer numbers in culture collections. Consequently, their industrial 

 potential is less understood than that of the Moniliales. Poor sporula- 

 tion in culture often is due to the use of media too rich in nutrients. 

 Where this is true, as with many pycnidial strains, such weak but 

 natural media as hay extract agar, soil extract agar, or cornmeal agar 

 markedly increase sporulation. 



A few of the imperfect fungi have long been used commercially for 

 the manufacture of cheese and the production of citric acid, but it was 

 the antibiotics industry that stimulated fermentation research to ex- 



