Zygnemacese 



333 



and they may be either lateral or terminal. In Spirogyra they may arise by 

 a modification 'of a conjugation-tube which has been protruded by a cell some 

 distance removed from those cells actually engaged in conjugation (West, '91 ; 

 Borge, '94). The chloroplasts of those cells which have developed rhizoids 



Fig. 209. A, young filament of Mougeotia sp. showing basal organ of attachment, x 100. 



B, Mougeotia capucina (Bory) Ag. showing the edge of the plate-like chloroplast, x 430. 



C, M. viridis (Kiitz.) Wittr., vegetative cells, x 445. D H, M.parvula Hass., x 445. /, M. 

 gracillima (Hass.) Wittr., x 445. 



are often irregular and they frequently degenerate. In Spirogyra the nucleus 

 may also disappear, this taking place as a rule before the degeneration of the 

 chloroplasts begins. 



