142 



PHAEOPHYCEAE 



sporangia of the plethysmothallus young macroscopic Eudesme 

 plants appear, so that it may be assumed that there is a definite 

 akernation of generations in which the small gametophyte forms the 

 winter phase. 



"NEDULLft- 



Fig. 95, Eudesme virescens. A, plant. B, diagram to illustrate thallus construc- 

 tion (multiple strand type). C.i7. = colourless hair, P.^. = primary assimilator, 

 »S.^. = secondary assimilator, 5'.C. = secondar>' cortex, 5'.-S'c. = secondary sub- 

 cortex, S.M. = secondary medulla. C, apex ( x 160). D, thallus with branch and 

 corticating filament ( x 75). E, unilocular sporangia. F, plurilocular sporangia. 

 (A, E, F, after Oltmanns; B-D, after Parke.) 



Mesogloiaceae : Chordaria (a small cord). Fig. 96. 



In Mesogloia there is a single central filament whilst in Eudesme 

 there are several, but in Chordaria development has proceeded a 

 stage farther and the branched cartilaginous fronds possess a firm, 



