88 THE ALGAE 



has shown that in one species, S. coalita, the asexual generation is 

 the small endophyte Codiolum petrocelidis (Fan, 1959). Both this 

 and Acrosiphonia differ from Cladophora in their cell wall material 

 which is a further reason for treating them as separate genera. 



Anadyomenaceae : Microdictyon {micro ^ small; dictyon, net). Fig. 



47 

 Branching in these plants is usually multiple in one plane, 

 and sooner or later cells of the branches become attached to 



those of other branches by means 

 of special pads or tenaculae, 

 so that a flat net-like thallus 

 eventually results. M. mutabile 

 from New Zealand can exist in 

 a spongiose form with very few 

 anastomoses so that it can easily 

 be mistaken for a coarse species 

 of Cladophora^ but it also gives 

 rise to the typical net thallus. 

 In those species that have been 



Fig. 47 Portion of net of Af/croJ/cf- investigated, sexual reproduction 

 3;onwMfa^?//g(x 24). (After DeUow.) jg isogamous and there is alter- 

 nation of isomorphic generations. The same is also true of 

 Anadyomene stellata. 



Siphonocladaceae: Cladophoropsis (like Cladophora). Fig. 48 



As the name impUes, the species are very Uke those of Clado- 

 phora from which they differ, however, in the more or less general 

 lack of a cell wall at the base of branches and also in possessing true 

 segregative division within the cells, the contents of one cell round- 

 ing off into two or more portions which become cut off by new 

 walls. In more advanced members of the family, e.g. SiphonocladuSy 

 the cell walls are even fewer. 



* Valoniaceae: Valonia (after the Valoni, an Itahan race). *Sea- 

 bottle'. Fig. 49 



In this genus, which is restricted to warm waters, the young 

 coenocyte consists of one large vesicle whilst the old one becomes 

 divided up into a number of multinucleate segments. It has been 

 suggested (cf. p. 426) that it should really be regarded as a coeno- 



