CERAMIALES 



231 



are re-developed in the spring. The main axes and branches are 

 corticate or ecorticate, and possess a polysiphonous appearance due 

 to the single axial cell series being surrounded by four to twenty- 

 four pericentral cells or siphons. The corticating cells, when 

 present, are always shorter and smaller and are often only found 

 in the basal portions of the stem. The ultimate branches are not 



Iw 





Fig. 153. Janczeivskia. A, J. moriformis on Chondria sp. ( x 6). B, filaments of 

 J. lappacea in host, Chondria nidifica ( x 180). C, longitudinal section of cystocarp 

 of y. moriformis (xi8o). D, antheridial conceptacle of J. lappacea (xiSo). 

 (After Setchell.) 



polysiphonous and frequently terminate in delicate multicellular 

 hairs. 



The colourless antheridia, which are formed in clusters, are borne 

 on a short stalk that morphologically is a rudimentary hair. In 

 Polysiphonia violacea, where the haploid number of chromosomes 

 is twenty, the two basal cells of the hair are sterile, the upper one 

 giving rise to a fertile polysiphonous branch and a sterile hair. One 

 or more mother cells are formed from all the pericentral cells on 

 the fertile branch, and each mother cell produces four antheridia 



