SOIL FUNGI 249 



Thamnidiaceae. Species of Thamnidium (T. elegans) 

 have been isolated from the soil by Jensen, Dale, Pratt 

 and others. 



3'. Sporangia of one kind only, multispored : the membrane is 

 for the major part solid, persistent, of a very dark 

 blackish color, or is swelling only toward the base. 

 Sometimes the sporangium dissolves simply, leaving 

 the columella, while at other times it is thrown off at 

 the same time as the columella and opens only after 

 swelling of the membrane. Pilobolaceae. Species of 

 Pilobolus have been isolated by Oudemans and Koning 

 from soil and Povah from horse manure. 



4'. Sporangia without a columella, with a diffluent dis- 

 appearing membrane, as in the case of the Mucoraceae. 

 Zygospores enclosed singly in a carposporium. Mort- 

 ierellaceae. Several species of Mortierella have 

 been found in the soil by Oudemans and Koning. 

 The last 3 genera are not of common occurrence in the 

 soil; however, they are found abundantly on rotting 

 manure and are thus readily introduced into the soil. 

 2. Reproduction asexually by conidia produced either solitary 



or in chains, sporangia not produced, suborder Conidio- 



phorae. 



1'. Conidia solitary, spherical or oval, borne on conidio- 

 phores swollen in the middle or at the extremity. 

 Chaetocladiaceae. 



(a) Conidiophores branched dichotomously in bunches 



or arranged irregularly. Round or oval conidia 

 are borne around a spherical head. Cunning- 

 hamella (No. 93, PI. XIII). C. elegans has been 

 isolated from the soil by Lendner, Povah, and 

 others. 



(b) Conidiophores verticiliately branched, swollen 



into small heads furnished with sterile threads. 

 Chaetocladium. 

 2'. Conidia in chains: 



(a) Conidiophores not swollen at tip. Piptocephalis. 



(b) Conidiophores swollen at apex: 



(a') Conidiophores not branched. Syncephalis. 

 (b') Conidiophores branched. Syncephalaslrum. 

 The last 4 genera are only rarely found in the soil. 

 B. ASCOMYCETES. Mycelium multicellular. The group is characterized 

 by the formation of an ascus or sac which usually contains eight spores; 

 these asci are assumed to represent a "perfect" stage, in some cases 

 certainly developed subsequent to fertilization; the fruiting masses con- 

 taining the asci are very variable. 



