ECTOCARPALES 



147 



plants with plurilocular sporangia, give rise to haploid zooids, and 

 these develop into a thread-like gametophytic plant bearing long 

 filaments, the possession of this type of gametophyte indicating 

 that the genus is perhaps more closely allied to the Mesogloiaceae 

 than to the Ectocarpaceae. 



Spermatochnaceae : Spermatochnus (sperma, seed; tochniis, fine 

 down). Fig. 100. 



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

 cylindrical, branched thallus being derived primarily from a central 



E A B C 



Fig. 100. Spermatochnus paradoxus. A, plant ( x 0-44). B, apex of young plant 

 showing origin of cortication. C, portion of old thallus showing structure, 

 a = assimilator, c = cortical cells, c/= central filament, /i = hair, m = mucilage. 

 D, portion of thallus showing cortication and pairs. E, paraphyses and unilocular 

 sporangia ( x 200). (A, E, after Newton; B-D, after Oltmanns.) 



axis composed 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 grov^h of the cortex is secured by tangential division of the 

 primary corticating cells, though later more filaments may grow on 

 top of them. The outermost layer of the cortex bears the assimi- 

 latory filaments and hairs. As the plants become older mucilage 

 develops internally and forces the cortex away from the primary 

 central filament although a connexion is maintained by the threads 



10 .2 



