Fig. 86 Myrionema strangulans. A, young plant ( x 640). B, 

 plurilocular sporangia ( x 340). C, unilocular sporangia ( x 340). D, 

 ii-day-old plant from zoid of unilocular sporangium ( x 336). 



(After KyHn.) 



gested that some of the other species placed in the genus or in aUied 

 genera may have isomorphic alternation in which case they may 

 need to be removed to the Ectocarpales. 



Spermatochnaceae : Spermatochnus {sperma^ seed; chnus^ fine 

 down). Fig. 87 

 This is essentially one of the corticated types, the filamentous, 

 cyUndrical, branched thallus being derived from a central axis com- 

 posed of a single filament with a definite apical cell. Each individual 

 cell of this filament segments at one end and so definite nodes are 

 formed. The corticating filaments arise from the nodes, and growth 

 of the cortex is secured by tangential division of the primary corti- 

 cating cells, though later more filaments may grow on top of them. 

 The outermost layer of the cortex bears the assimilatory filaments 

 and hairs. As the plants become older mucilage develops internally 

 and forces the cortex away from the primary central filament al- 

 though a connexion is maintained by the threads from each node. 

 Unilocular sporangia, together with clavate paraphyses, develop in 

 sori, the sporangia arising from the base of the sterile threads. The 



157 



