48 THE FLORA OF NEBRASKA. 



Family.— MUCORACEAE.* 



"Mycelium well developed, thread-like (i. e., with hyphae), branched, up to the time 

 of fructification unicellular (i. e., without septa). Asexual reproduction by internal 

 spore-formation in terminal cells (sporangia) or by reduced sporangia which resemble 

 one-celled conidia or conidia-chains. Sexual spore-formation by zygospores; that is, by 

 the union of two undifferentiated or scarcely differentiated cells to form a zygospore. 

 All spores germinating by a germinating tube; no swarmspore formation." — (Schroeter). 



The Mucoraceae are a well marked group containing about 18 genera and 120-12S 

 species, which are saprophytes or parasites on other fungi, chiefly of the same group. 

 The group is now divided into 5 sub-families, of w r hich 2 only are represented in Ne- 

 braska. 



In the formation of zygospores the Mucoraceae agree with the Conjugatae. All of 

 the sub-families except the Cephalideae form the zygospore directly by the union of the 

 contents of the two conjugating cells, as in the Zygnemeae. In the Cephalideae the 

 zygospore is formed in a new cell cut off by a partition wall from the cell formed by the 

 conjugating cells, as in the Mesocarpeae. But the asexual spore-formation has no proto- 

 type in the Conjugatae. In this respect the Mucoraceae appear to be connected with the 

 Chytridiaceae, certain forms of which (Zygochytrium) bear a remarkable resemblance to 

 them both in their sexual and asexual reproduction. 



SYNOPSIS. 



Asexual spores formed in sporangia. 



Sporangia with a columella Sub-family Mucoreae 



Mycelium and sporangia of one kind only Tribe Eumucoreae 



Sporangiophore simple or branched Mucor 



[Aerial mycelium thorny Spinellus] 



[Sporangiophore dichotomously branched at apex Syzygites] 



Sporangiophore unbranched, bright metallic in color Phy corny ces 



Mycelium of two kinds— vegetative and fertile. Sporangia of one kind, 



Tribe Rhizopeae 

 Membrane of sporangium entirely disappearing, leaving the colu- 

 mella, which soon collapses Ascophora 



Membrane of sporangium of two parts: above cuticularized and perma- 

 nent, below thin and quickly disappearing Tribe Piloboleae 



Sporangiophore swollen below the sporangium Hydrogera 



[Sporangia without a columella, fertile mycelium distinct from vegetative, 



Sub-family Mortierelleae] 

 Asexual spores formed as conidia. 



Conidia single — i. e., not in chains Sub-family Chaetocladieae 



Parasitic on other Mucoraceae Chaetocladium 



Sub-fam. — Mucoreae. — Asexual spores formed in sporangia; sporangia with a 

 columella (except sporangiola in forms having them); zygospores naked, 

 or surrounded by loose, simple, or slightly branched hyphae. 



Tribe. — Eumucoreae.— Mycelium of one kind only. 



This is the typical group from which all the others, unless perhaps the Cepha- 

 lideae, appear to be derived. 



* By Roecoe Pound. 



