i8 



MORPHOLOGY AND CULTURE OF MICROORGANISMS. 



very moist conditions or in substrata with high water content. Rhizopus 

 is a very common contamination in laboratory cultures. 



There are many common species of the genus Mucor, very few of 

 which are identifiable without critical study. The specific names as 

 commonly cited often designate groups of species or varieties rather than 

 sharply marked forms. Certain of these may be briefly considered. 



Mucor mucedo L. is a common form upon dung, characterized by 

 heads (sporangia) upon long sporangiophores,* at first yellow then becom- 



FIG. 2. Mucorinece. Mucor. From Tabulae Botknica, showing sporangia origi- 

 nating from mycelium, spores and spore germination, and the formation of zygospores 

 in a heterothallic species (diagrammatic). (Reduced one-half). (By permission of 

 A.F.Blaskeslee.) 



ing dark brown or black and studded upon the surface with needles of 

 lime. 



Mucor racemosus, Fresenius, is characterized by the production of 

 chlamydospores or cysts in the mycelium within the substratum, as 

 elliptical thick-walled cells. The sporangiophores typically branch to 

 make racemes of sporangia. The racemose mucors are active agents in 



*The term sporangiophore is composed of the word sporangium combined with the suffix 

 phore, meaning bearer. In sympodial branching the first fruit is on the tip of the original hypha, 

 the first branch arises below this fruit and is terminated by the second fruit. Each successive 

 branch and fruit originates in similar manner. 



