60 



AGRICULTURAL AND INDUSTRIAL BACTERIOLOGY 



Its pporangiophores are sometimes branched, do not arise in 

 clusters, and no rhizoids are developed. In the sporangium 

 the columella is not attached to the sporangium wall, but 

 may be spherical in shape, pear-shaped, and in one species 

 pointed or covered with spines. The various species of 



Fig. 40. — Common species op mucok. a. Sporangiophore showing 

 branching and grouping of sporangia, b. Longitudinal section 

 through sporangium, c. Spores, d. Columella. 1. ilucor hie- 

 malis. 2. Mucor piriformis. 3. Mucor mucerlo. 4. Mucor plumr 

 beus. 5 Mucor alternans. ( 1, 2, 3, after Wehmer. 4, 5, after 

 Gray.) 



Mucor are separated from each other on the basis of 

 the size, shape, and color of the sporangium, size and 

 shape of columella, and the branching of the sporangio- 

 phores. 



Some eleven species of Mucor have been described and are 

 comparatively common. They may be differentiated from 

 each other by use of the key given in the footnote.^ 



1 Key to Species of Mucob 

 A. Sporangiophores rarely or never branched. 



B. Columella spherical Muoor hiemalis. 



BB. Columella pear-shaped (piriform) M. piriformis. 



BBB. Columella elongate to ellipsoidal M. rruucedo. 



AA. Sporangiophores usually branched. 



B. Columella usually knobbed or spiny near tip. . M. plumbeus. 

 BB. Columella not roughened at tip. 



C. Rarely fruiting at room temperatures, im- 

 portant in commercial alcohol manufac- 

 ture, rapidly saccharifying starch M. rouxii, 



OC. Readily fruiting at room temperature, 

 not commercial types. 



D. Sporangiophores with definite main 

 stem and secondary lateral branches, 

 racemose. 



E. Columella ovoid M. racemosus. 



EE. Columella spherical 



