66 THE FUNGI WHICH CAUSE PLANT DISEASE 



Fruiting mycelium multicellular, 

 some cells forming sporangia, 

 others producing gametes and 



oospores 2. Ancylistidiales. 



Mycelium well developed 

 Fertilization by motile sperms. ... 3. Monoblepharidiales. 

 Fertilization through an anther- 



idial tube 4. Saprolegniales, p. 74. 



Conidia present 5. Peronosporales, p. 77. 



Sexual spores isogamous, formed by the 



union of similar gametes.. Subclass II. Zygomycetes, p. 101. 

 Asexual spores several, in sporangia. . . 6. Mucorales, p. 102. 

 Asexual spores solitary, conidia 7. Entomophthorales,p. 107. 



Of these orders the Ancylistidiales which are parasitic upon 

 Algae, and the Monoblepharidiales which are saprophytic will not 

 be considered further. 



Subclass Oomycetes (p. 65) 



In the Oomycetes there is pronounced difference between the 

 male and female sexual organs. The oSgonium is comparatively 

 large, and contains one or more large passive eggs (oospheres), 

 which are fertilized by sperms, differentiated or not, which either 

 swim to the oogonium by cilia, creep to it, or are carried to it by 

 a fertilizing tube. Oospores are in some species produced fre- 

 quently and abundantly while in others they are entirely unknown. 

 The asexual reproduction is by either conidia or sporangia. 



Chytridiales (p. 65) 



The members of this order are the simplest of any of the Phy- 

 comycetes. Many of them are single, more or less globose, undif- 

 ferentiated cells, others have a more or less prominent haustoria- 

 like mycelium, while but few have any approach to a true myce- 

 lial development. Most are intracellular parasites; a few of the 

 more highly developed genera are intercellular parasites. With 

 few exceptions reproduction is entirely asexual, all spores being 

 formed directly from the vegetative cell. Zoosporangia and thick- 



