92 SEAWEEDS 



branching filaments (fferponcma), and this cushion- 

 like thallus grows by the division of the peripheral 

 cells. The assimilative filaments arise in centrifugal 

 order, and grow by the division of their apical cells 

 or their upper cells. 



The Reproductive Organs. The unilocular spor- 

 angia occur mostly singly, not in sori, but fairly 

 evenly distributed over the thallus, and either as 

 lateral out-growths of assimilative filaments or in 

 place of these. In Myrionema they spring directly 

 from the basal cushion. They are relatively large, 



FIG. 22. Chordaria divaricata. Transverse section of part of thallus, 

 showing sporangia. Highly magnified. (After Eeinke.) 



and vary in form from oval, obovate, clavate, to cylin- 

 drical, with irregular lateral protuberances (Petro- 

 spongium). The plurilocular sporangia are of diverse 

 origin, as stated above, and have sometimes one, 

 sometimes several rows of loculi. 



The genera composing the Chordariacece have been 

 placed in many different orders by recent authors, 

 and though no great degree of natural affinity can be 

 claimed for the group as it stands, there are certain 

 merits of simplicity in its favour, as a provisional 

 group at all events. 



