MUCORALES 115 



Producing lesions in the cornea, Italy. 



Mycelium loosely interwoven, white, cinereous-plumbeous on milk, bread, 

 and potato; growth abundant at 37° C, very slow at 15° C, and at 51° C. ; 

 sterile hypliae large, branched, 14-15/* in diameter, hyaline, corymbose or 

 racemose branched at the tips ; branches of sporangiophores either alternate 

 or opposite, simple or dichotomous, 80-300 x 7-8/i., leaving the main axis at 

 about an angle of 45° slightly enlarged at the tips; sporangia spheric or sub- 

 spheric with a thin membrane 40-44/t in diameter (rarely up to 50-55/a or as 

 small as 15-22/a), columella obovate, pyriform, more or less light fuscous, 

 22-24/x broad ; spores thin-walled, hyaline becoming light yellowish, spherical, 

 4-4. 5/a, rarely ovoid, zygospores unknown. 



RHIZOPUS 



Rhizopus Bhrenberg, Nova Acta Acad. Leopold. 10: 198, 1820. 



Bhizomucor Lucet & Costantin, Rev. Gen. Bot. 12 : 81, 1900. 



The type species is Rhizopus nigricans Ehrenberg. The type of Rhizomucor 

 is R. parasiticus Lucet & Costantin. 



Aerial mycelium of creeping stolons, with holdfasts at the nodes which at- 

 tach the hyphae to the substrate. Sporangiophores arising in groups at the 

 nodes, sometimes solitary, enlarged above into a columella, as in Absidia. Spo- 

 rangia white at first, becoming black ; spherical or nearly so with base slightly 

 flattened ; membrane not cuticular, uniformly incrusted and entirely diffluent 

 without leaving a basal collar. Columella hemispheric, often flattening after 

 dehiscence, suggesting the pileus of a mushroom. Spores spherical or ovoid, 

 even angular, hyaline or brownish, cuticular walls, smooth or striate, rarely 

 spinulose. Zygospores without covering from outgrowth of suspensors, form- 

 ing in the substrate and on the stolons. Suspensors straight, swollen, without 

 appendages. 



Key to Pathog-enic Species 



Spores irregular, angular, subspheric, oval. B. parasiticus. 

 Spores spherical, smooth or echinulate, but not angular. 



Columella conici or subcylindric (black tongue). E. mger. 

 Columella ovoid or pyriform, pathogenic for rabbit. 



Clilamydospores not produced. E. rhizopodiformis. 



Chlamydospores present. E. equinus. 



Rhizopus equinus Costantin & Lucet, Bull. Soc. Myc. France 19: 200, 1903. 



Isolated from a horse, pathogenic for rabbit. Found in generalized in- 

 fection in swine by M. Christiansen (1922) and in bovine fetal membranes 

 and fetus by Theobald Smith (1920) who referred his species to R. rhizo- 

 podiformis. 



Mycelium at first white, then gray after the formation of sporangia. Spo- 

 rangiophores at first isolated and without rhizoids, straight or curved, later in 

 bouquets, frequently provided with rhizoids, cutinized, pale ochraceous ; 50-220/i, 

 sometimes up to 600/x long, 3-12.3/a in diameter. Sporangia 30-115/x in di- 



