146 



PHAEOPHYCEAE 



arise from the base of the short filaments or paraphyses. The zooids 

 from the unilocular sporangia germinate in late autumn to give a 

 branched, thread-like, microscopic gametophyte which persists 

 throughout the winter. In late winter and spring plurilocular 

 sporangia develop on the minute gametophytes, and when the 

 zooids have been liberated they fuse and the zygote germinates into 

 a new macroscopic Elachista plant. 



Myrionemaceae : Myrionema (myrio, numerous; nema, thread). 

 Fig. 99. 



The various species are epiphytic upon other algae, forming thin 

 expansions or minute flattened cushions or disks that are very 



Fig- 99- Myrionema strangulafis. A, young plant ( x 640). B, plurilocular 

 sporangia ( x 340). C, unilocular sporangia ( x 340). D, 11 -day-old plant from 

 zoid of unilocular sporangium ( x 336). (After Kylin.) 



variable in shape and from which numerous, closely packed, erect 

 filaments and hairs arise. M. strangulans is especially common on 

 sheets of Ulva during the summer. The basal portion of the 

 thallus has a marginal growing region and is composed of crowded 

 radiating filaments that may, on rare occasions, penetrate the host 

 plant. The unilocular sporangia, which are not borne on the same 



