63 



and are set free by the dissolution of the cell-walls. 

 The sporangia occur in clusters in Padina and 

 Taonia. and in scattered fashion in Didyota. The 

 prevailing number of spores is four, but frequently 

 only two, or rarely one. The division into four is 

 either simultaneous, when the resulting arrangement 

 is that of a tetrad, or by two successive bipartitions, 

 when the four spores lie in one plane. The spores 

 escape by an apical opening of the sporangial wall, 

 are motionless, and at first without a membrane. 

 They soon, however, secrete a cell- wall and germinate. 

 The process of germination, so far as it has been 

 observed, is the same for spores and oospores, but 

 the product of germination is either directly (Didyota 

 and Zonaria) a small plantlet of the parent form, or 

 (Padina, Taonia, and Didyopteris) a protonema-like 

 body from the superficial cells of which one or more 

 shoots arise in the form of the parent plant. 



None of the PhceopTiycece have caused greater 

 diversity of opinion as to their relationship than the 

 Didyotacece. Some authors have gone so far as to 

 place them with the Floridece or in a position apart 

 from the Phceophycece but pointing towards the 

 Floridece, and this indeed appears to be the favourite 

 view of their character, especially with those who 

 demand a link between Phceopkycece and Floridece 

 (though such a link might perhaps better be sought 

 lower in the scale than the Didyotacece}. This 

 opinion is based on the unciliated character of all 

 the reproductive bodies, the resemblance of the 

 motionless antherozoids to the pollinoids of Floridece, 

 and the division into four of the spores constituting 



