152 PLANT LIFE. 



and the Mycomycetes, where the sexual phase is completely 

 arrested, and consequently propagated exclusively by 

 asexually-formed spores. Each primary group is further 

 divided into two sections ; in the Phycomycet.es we have 

 the Zygomycetes, producing zygospores by conjugation, and 

 the Oomycetes, producing oospheres that are fertilized by 

 motile antherozoids, or by transfusion of the contents of 

 passive antheridia. In the Mycomycetes the Ascomycetes have 

 spores produced in asci — ascospores — the Basidiomycetes 

 form naked spores on basidia — basidiospores. 



The UstilaginecR or smut-fungi are considered as forming 

 a transition from the Phycomycetes to the Mycomycetes. The 

 above arrangement may be represented as follows — • 



PHYCOMYCETES. 



Zygomycetes. Oomycetes. 



MYCOMYCETES. 

 TTstilagineae. 



Ascomycetes. Basidiomycetes. 



The two modes of reproduction are not produced by 

 every species. In the Phycomycetes the asexual method is 

 more constant throughout the group than the sexual, although 

 in some species the latter method is the only one known. 



In the Mycomycetes the most complex sporophores pro- 

 duce spores in asci or on basidia ; but in numerous species 



