MUCORALES 109 



Although some of the following characters are often unstable, they should 

 be noted in the study of the Mucorales. The presence or absence of branching 

 is often difficult to determine. Sometimes typical branching may be found in 

 the small sporangiophores next the substrate, when it is not observed in the 

 larger sporangiophores. If stolons arc present, note their arrangement and 

 the disposition of the sporangiophores upon them ; also note the presence of 

 holdfasts, etc. The nature of the medium influences the height of the spo- 

 rangiophore, which should be determined only in cultures where optimum con- 

 ditions of growth prevail. Malt gelatin (10%) or 10% gelatin to which has been 

 added the residue of white wine from which the alcohol has been distilled, are 

 suitable. The latter is known as Lendner's medium. Report the height of the spo- 

 rangiophore from a colony cultivated at room temperature for at least 8 days, its 

 diameter, the diameter of the sporangium (one of the larger ones), the height 

 and diameter of the columella, the mean diameter of the spores (or their mean 

 dimensions), and the diameter of zygospores and chlamydospores. The spo- 

 rangial membrane may be diffluent, in which case, younger sporangia should 

 be measured, or the sporangia mounted in a mixture of glycerol and water. 

 If the membrane easily becomes fragmented, this should be noted. Note the 

 presence or absence of a collar about the columella and the surface of the 

 latter. Spore shape varies in the same sporangium. When a species is re- 

 ported as having spherical spores, the majority are spherical, although oval 

 or irregular spores may be present. Disregard variations in size unless they 

 are extreme. To find hypnospores use cultures 2 weeks old or more on solid 

 media or on liquid media with much sugar for sprouting cells. Note fermenta- 

 tions in case the sprout cells are abundant. 



Classification. — There is still considerable disagreement among mycologists 

 as to the subdivisions of this order. It is clearly divisible into three groups 

 which the older mycologists considered families (Mucoraceae, Endogonaeeae, 

 and Entomophthoraeeae). Some of the younger generation would elevate the 

 old families to suborders, the latter two suborders containing a single family 

 each, while the old tribes of the Mucoraceae are elevated to family rank 

 (Fritzpatrick 1930). In any case only members of the tribe IMucoreae and 

 Mortierelleae have so far been reported pathogenic and need be considered 

 here. Since many of the saprophytic genera are difficult to define, and there 

 are strong differences of opinion on synonymy, only the pathogenic genera 

 which have been reported pathogenic to mammals are included in the fol- 

 lowing kej^s. 



MUCORACEAE 



Mycelium coenoeytic, forming loose felted colonies ; sporangiophores erect, 

 often variously branched ; sporangia usually with a columella (absent in 

 Moriierella) ; sporangiophores abundant in the Mucoreae, in other tribes often 

 reduced to a few spores in small sporangioles ; zygospores resulting from the 

 copulation of gametangia. 



