MUCOR. 207 



Amongst other moulds standing in close relationship to 

 the Mucor species, Phycomyces nitens is frequently referred 

 to in the literature of this subject. It usually occurs on oily 

 substrata, but also on bread, excrement, etc. It resembles 

 Mucor, and its olive green sporangiophores with their metallic 

 lustre attain to an extraordinary size. The sporangium is 

 t>lack, the columella pear-shaped, and the spores yellowish. 



Thamnidium elegans (Fig. 39) frequently occurring on the 

 dung of various animals, on bread, etc., is a fine mould with 

 sporangia recalling those of Mucor ; but in addition to the 

 terminal sporangium formed at the apex of the main sporangio- 

 phore, the latter gives rise to a number of forked side branches, 

 on which sessile sporangia (sporangioles) are formed without 

 columella and with fewer spores. 



In conclusion, we may allude to Sporodinia grandis, a fungus 

 often met with on toadstools growing in woods. It forms a 

 dense felt of branching hyphae with numerous sporangia, and 

 also produces zygospores. 



Hansen's determination of the limits of temperature for 

 the three species, M. racemosus, neglectus, and alpinus, when 

 grown on wort-agar gelatine and in wort, proved that the 

 formation of sporangia and zygospores can go on at a slightly 

 lower maximum than is required for vegetative growth (the 

 behaviour is thus analogous to that of the Saccharomycetes). 

 The development of sporangia can, however, go on at the same 

 minimum as that required for vegetative growth. The species 

 vary with regard to the temperature limits for sporangia, on 

 the one hand, and for zygospores, on the other ; thus M. 

 -alpinus exhibits a higher maximum for the formation of 

 sporangia than of zygospores, but the reverse is the case 

 with M. neglectus. It follows that the temperature limits 

 may serve to determine the species. Mucor racemosus, for 

 example, when grown on the media alluded to, gives as limits 

 for vegetative growth a maximum of 32-33 C., and a 

 minimum of 0-5 C. ; M . alpinus a maximum of 29-31 C., 

 and a minimum of 0-5 C. ; M . neglectus, maximum 33 C., and 

 minimum 3 C. 



The Mucor species are of special interest to us, because 

 they can act, in varying degrees, as true alcoholic ferments. 



