MUCORALES IN FAMILIES OTHER THAN MUCORACEAE 91 



therefore homothallic. But there is some apparent differentiation of 

 the conjugating branches, one being larger than the other; only the 

 larger branch develops into a suspensor. This condition then rather 

 approaches the formation of oospores in Saprolegnia (compare Fig. 

 41 with Fig. 24). Zygorrhynchus is an exception to the isogamy 

 general in the INIucorales. 



Zygorrhynchus Moelleri is one of the most important of the Phyco- 

 mycetes found in the soil. It is particularly abundant in loose sandy 



Fig. 41. Zygorrhynchus Moelleri: a, sporangiophore ; h, columellae; c, spo- 

 rangiospores; d, chlamydospores in submerged mycelium; e, zygospore. 



soils, sometimes forming enough mycelium to bind the loose particles 

 together. In subsoils it is frequently the only fungus present. Soils 

 poor in organic matter seem then to be especially favorable for its 

 growth. It is active in ammonification, but does not decompose 

 cellulose. 



Circinella. In Circinella the sporangia are formed only on lateral 

 branches, not at the tips of the sporangiophores. These lateral 

 branches frequently arise in whorls, six or eight branches arising 

 from one point at regular intervals along the aerial filaments of 

 mycelium. These lateral branches are also peculiarly curved upon 

 themselves, a condition which is also found in Mucor circinelloides 

 (Fig. 38). Species of Circinella are frequently found on the drop- 

 pings of various animals. 



Mucorales in Families Other than Mucoraceae. Thamnidium is the 

 only member of the Thamnidiaceae frequently encountered. It has 



