86 



MOLDS BELONGING TO THE PHYCOMYCETES 



Fig. 35. Mucor hiemalis: a, 

 sporangiophores ; b, sporan- 

 gium; c, columellae; d, spores. 



There are many kinds of Mucor that, are worthy of specific rank 

 even to a conservative taxonomist, but owing to the large number 

 of species (Lendner recognizes 51 species, Naumov 93 species and 

 several varieties, and Zycha 42 species) keys for identification are 

 not given here, but reference is made to the original monographs. 



Lendner's key, in its essential points, is 

 given in the first edition of this book 

 and in Oilman and Abbott's ^ paper on 

 soil fungi. In some ways the keys and 

 description of species by Naumov and 

 particularly by Zycha seem to be pref- 

 erable. Keys based on this system will 

 be found in Oilman,- but those in the 

 original Zycha are more complete. 

 The characters used for identification naturally vary with differ- 

 ent authors. Lendner's system which has heretofore been generally 

 followed uses as important characters for classification the occur- 

 rence of branching of the sporangiophores, their height and thickness, 

 the diameter of the sporangium, the length and thickness of the 

 columella, the dimensions of the spores, the degree of diffluence of 

 the sporangial membrane, the form of the columella, and the shape 

 of the spores. Since zygospores are so 

 rarely formed in cultures, they cannot 

 usually be used in diagnosis. Many of 

 the characters given above are obviously 

 subject to considerable variation even 

 in a single individual and cannot be 

 relied upon too much. The occurrence 

 of branching of the sporangiophore is 

 the most important single character. It 

 cannot be easily determined in many 

 cultures because of the close inter- 

 twining of the hyphae. The develop- 

 ing sporangiophores are frequently un- 

 branched; therefore, one cannot rely 

 upon observations made at the edge 

 of the growing colony where the 

 mycelium is not so dense. Branching is best observed in slide cul- 

 tures of the type shown in Fig. 29. A binocular dissecting micro- 

 scope is of gi-eat value. Three main types of branching are recog- 

 nized: the Monomucors with unbranched sporangiophores, as in 

 Fig. 35; the Racemomucors, with racemosely branched sporangio- 



FiG. 36. Mucor racemosus: a, 

 sporangiophore; b, sporangium; 

 c, columellae; d, spores; e, 

 chlamydospores on the aerial 

 mycelium ; /, chlamydospores 

 on the submersed mycelium. 



