ft 



KEYS TO THE FAMILIES AND MORE IMPORTANT GENERA OF MUCORALES 183 



Only asexual reproduction has been observed so far. In hyphal outgrowths 

 from short one- celled thalli within the host are produced a few to numer- 

 ous endoconidia with definite thin walls. These are pushed out several 

 at a time at short intervals until all have been discharged. In germination 

 they produce a small sticky knob by which they become attached to the 

 living nematode host, into whose body a germ tube penetrates and then 

 divides repeatedly to form the unicellular thaUi. Possibly this fungus may 

 have some relationship to this order. 



Keys to the Families and More Important Genera of Mucorales 



Key to the Families of Order Mucorales 

 Asexual sporangia, sporangioles or "conidia" aerial. 

 All the sporangia many-spored, with a well-developed columella; sporangium 

 wall relatively thin and breaking or deliquescent. 



Family Mucoraceae 

 All the sporangia many-spored, with a moderate-sized columella; sporangium 

 wall thickened above and not breaking up or deliquescent. 



Family Pilobolaceae 

 Terminal primary sporangium of the sporangiophore many-spored, with a 

 well-developed columella; sporangium wall thin and breaking up or deli- 

 quescent; secondary sporangia in the form of few-celled or one-celled 

 sporangioles which are usually indehiscent. Primary sporangia lacking 

 under unfavorable conditions, and never formed in a few genera. 

 Sporangioles on more or less dichotomous branches formed laterally along 

 the main sporangiophore. (Primary sporangium lacking in the genus 

 Chaetocladium.) Family Thamnidiaceae 



Sporangioles on the surface of rounded or elongated heads terminating 

 sporangiophores apart from the primary sporangiophore. Primary spo- 

 rangium lacking in the genera Cunninghamella, Mycotypha, etc. 



Family Choanephoraceae 

 Sporangia spherical, many-spored, with a basal septum and no columella. 



Family Mortierellaceae 

 Sporangia narrow, one- to several-spored, with no columella, usually more or 

 less capitately borne, often breaking apart into one-spored segments. 



Family Piptocephalidaceae 



Sporangia reduced to one-celled, indehiscent sporangioles ("conidia") borne 



singly on sterigmata arranged on one side of a branch ("sporocladium") 



so as to resemble a comb. Family Kickxellaceae 



Sporangia, zygospores and chlamydospores in the interior of rounded masses of 



hyphae; often buried in humus or soil. Family Endogonaceae 



Key to the More Important Genera of Family Mucoraceae 



Sporangiophores arising from the thin or thick mat of aerial mycelium, not from 



stolons. Not repeatedly forked dichotomousl^y. 

 . Primary sporangium present at the apex of the sporangiophore. 

 Sporangiophore tall, dark, unbranched, with metallic appearance. 



Phycomyces 

 Sporangiophore slender and uniformly thick its wliole length, unbranched, 

 or racemosely or cymosely branched— in the latter case the branches 



