Sumstine: North American Mucorales 147 



mining the line of cleavage between genera as well as between 

 species. 



The azygospores indicate a tendency to eliminate the sexual 

 method of reproduction. Investigation along this line may aid 

 in solving some problems in the evolution of plants and pos- 

 sibly determine more clearly the phylogeny of the Mucoraceae. 



In more than one half of the species there are also developed 

 oidiospores and chlamydospores. These may have some taxo- 

 nomic value when they are more clearly understood. 



The limits of this genus are possibly best left undetermined for 

 the present except as defined in the original description. It 

 seems that most of the species listed in Section 2, Racemo-Mucor, 

 by Fischer /. c. and Lendner /. c. should be placed in this genus. 



Key to the Species 

 Sporangiophores with short, straight or very slightly bent 



branches. i. C. ramosus. 



Sporangiophores with rather short circinate branches. 2. C. circinelloides. 



Sporangiophores with usually long branches. 



Columella globose or nearly so. 3. C. erectus. 



Columella piriform with spines. ■ 4. C. plumheus. 



Columella piriform without spines. 5. C. globosus. 



I. Calyptromyces ramosus Karst. /. c. 1849 

 ? Mucor juglandis Link, Ges. Naturf. Freunde Berl. Mag. 3: 

 30. 1809. 



? Mucor truncorum Link, Ges. Naturf. Freunde Berl. Mag. 3 : 



30. 1809. 

 Mucor racemosus Fres. /. c. 1850. 

 Pleurocystis Fresenii Bonord. /. c. 185 1. 

 Chlamydomucor racemosus Bref. /. c. 1890. 



Link describes two branching Mucors that seem to agree with 

 the species under consideration but it is impossible to say definitely 

 that his plants are identical with Karsten's plants. If these plants 

 are the same then Link's name would have to be substituted for 

 the name given above. 



The height of the sporangiophores varies from 5-50 mm. The 

 branches are usually short and straight. The columella may be 

 globose or oval. The spores globose or elliptical. The chlamy- 

 dospores and oidiospores are very numerous. Both zygospores 

 and azygospores have been observed. 



