B6 CLASSIFICATION AND TAXONOMY OF FUNGI 



13. Mycelium lacking, or consisting of delicate rhizoid-like 



threads Order Chytridiales 14 



14. Mycelium lacking, thallus at first naked and amoeboid; 



holocarpic, parasitic Suborder Alyxochytridineae 



14. Mycelium of delicate threads, thallus with cell wall 



from the first, sterile and fertile portions distinct 



Suborder Alycochytridineae 

 13. Mycelium a chain of cells, each a functional sporangium, 

 antheridium, or oogonium; zoospores biciliate 



Order Lagenidiales 

 11. Mycehum well developed, for the most part remaining vegeta- 

 tive; reproductive parts separated from assimilatory by septa 15 

 15. Sporangia of two kinds: thin-walled and thick-walled, re- 

 sistant; sexual reproduction lacking or involving fusion of 

 motile gametes forming motile zygote; zoospores uniciliate 



Order Blastocladiales 

 15. Thin-walled sporangia only; sexual spores thick-walled 16 



16. Gametangia dissimilar; fertihzation heterogamous to form 

 oospore, asexual spores motile Subclass Oomycetes 17 

 17. Antherozoids and zoospores uniciliate 



Order Monoblepharidales 

 17. Antherozoids absent; fertilization tube extends from 

 antheridium to oosphere 18 



18, Oospheres 1 to several in each oogonium, peri- 

 plasm absent; zoospores biciliate, commonly di- 

 planetic Order Saproleginales 



18. Oospheres 1 in each oogonium, periplasm present; 

 zoospores biciliate 19 



19. Thallus aquatic, saprophytic, arbusculate, 



branches constricted Order Leptomitales 



19. Thallus aquatic, not arbusculate nor con- 

 stricted, parasitic, zoospores extruded in a 

 vesicle Order Pythiales 



19. Thallus terrestrial, parasites on seed plants; 

 sporangia germinating by zoospores or germ 

 tube; oospores within host Order Peronosporales 

 16. Gametangia morphologically similar, fertilization isog- 

 amous to form zygospore; asexual spores conidia 



Subclass Zygomycetes 20 

 20. Saprophytes; sporangia from one to many-spored; 



conidia not forcibly liberated Order Alucorales 



20. Mostly parasites on insects; conidia forcibly dis- 

 charged; zygospores formed within hosts 



Order Entomophthorales 



