PH^OSPOREyE. 113 



The zoospores produced in the two forms of zoosporangia 

 present no observable differences in shape or size. Those 

 formed in the unilocular zoosporangia germinate directly, so 

 far as is known j while those from the multilocular zoospo- 

 rangia sometimes conjugate, and must then be considered 

 as zoogametes possessed of sexual functions. 



The sexual modes of reproduction met with in the 

 Phceosporece show an interesting sequence from the con- 

 jugation of precisely similar zoogametes, to the fertilization 

 of a large passive oosphere by motile antherozoids. 



In Edocarpus siliculosus the zoospores produced in 

 multilocular sporangia are alike in size and form, but some 

 of these presumably female zoogametes lose their cilia and 

 come to rest. In this condition they appear to exert an 

 attractive influence over the male zoogametes, which remain 

 active, and swarm round them until fertilization is effected 

 by the coalescence of the two forms, and after which a cell- 

 wall is formed and germination commences at once. 

 In cases where the female zoogamete is not fertilized 

 germination still takes place, as is also the case with those 

 male gametes that do not conjugate ; but the individuals 

 resulting from the germination of the latter soon perish. 

 The above example illustrates the gradual acquirement of 

 sexual functions by originally asexual organs of reproduction. 



The small group known as Cutkriacece, including the 

 genera Cutleria, Zanardinia and Agalozonia, are included 

 by Bennett in the Fhceosporece, on account of agreeing with 

 the latter in the asexual mode of reproduction by motile 

 zoospores. The general habit is also the same, but the 

 sexual mode of reproduction is marked by a decided 

 differentiation of the male and female organs, which as 

 explained above is indicated in Edocarpus, carried one step 



