60 MORPHOLOGY AND CULTURE OF MICROORGANISMS 



was applied by Hansen to one of these which is found frequently in 

 breweries. The genus Willia has been created for another series of 

 these forms. Another widely distributed species, Monilia sitophila, forms 

 loose salmon-pink masses of conidia on .the surface and in the interior of 

 bread, in cereals and other foods. In culture media Monilia sitophila 

 fills culture tubes and dishes with loose fluffy salmon masses of conidia. 

 This organism frequently overruns an incubator or a culture room in- 

 fecting everything fermentable. 



DEMATIUM. One species of Dematium, Dematium pullulans, has 

 been much studied. This is frequently found within decaying fruit as 

 dark brown colonies. In culture, mycelium is sparingly produced, 

 either colorless or colored, and conidia are borne in clusters and chains 

 all along the hyphae submerged in the substratum. At first both myce- 

 lium and conidia are colorless, later some or all of the cells develop 

 heavy dark brown walls. Although not active as an agent of fermen- 

 tation, it occurs very frequently in the fermentation industries some- 

 times discoloring the fermenting products. The conidia bud out from 

 the cells of the mycelium in a manner resembling the yeasts. Its 

 occurrence with the yeasts has led to many careful descriptions of its 

 several types of spore production and its biological activities. 



SAPROLEGNIACE/E. This is an aquatic group of Phy corny cetes, which 

 includes both saprophytes and parasites. Its commonest members 

 grow as shimmering masses of cottony mycelium upon the bodies of 

 flies or other insects in aquaria. Other members of the same group 

 are parasitic, some attacking young fish and producing characteristic 

 lesions. Both sexual and asexual spores (motile swarm spores) are 

 abundantly found. 



