CEdogoniacece 



59 



Asexual reproduction takes place by means of zoogonidia, which 

 are formed singly from ordinary vegetative cells. There is a re- 

 juvenescence of the entire cell-contents, a large rounded mass 

 being formed, which ultimately escapes. In (Edogonium this 

 process may take place in any of the vegetative cells of the 

 filament, whether terminal or not, 

 and it sometimes occurs in a 

 young plant consisting only of one 

 cell. The cell-wall splits into two 

 halves by a transverse slit near its 

 upper extremity and the rounded 

 mass of rej u venized protoplasm makes 

 its exit in a delicate hyaline vesicle. 

 This mass assumes a pyriform shape 

 and at the narrower end a small 

 colourless protuberance is formed, 

 round the base of which arises a 

 circle of numerous cilia (fig. 11 z). 

 This striking zoogonidium, which 

 may or may not possess a red pig- 

 ment spot, quickly swims away, the 

 entire process lasting only a few 

 minutes. On coming to rest it 

 attaches itself by its anterior hyaline 

 end, loses its cilia, and develops a 

 cell-wall. This cell ultimately forms 

 a new filament by transverse cell- 

 division (fig. 10 E I). The basal 



cell may be rounded and swollen or it may develop a hapteron or 

 organ of attachment (fig. 10 A D). 



Wille has observed resting-spores in some species of (Edogonium 1 . 



The sexual reproduction in this family of Algae presents a 

 greater specialization of the male and female organs than is found 

 in any other family of the green Algae. The oogonia may be 

 developed from any of the ordinary vegetative cells, and most 

 frequently arise from cells which exhibit intercalary surface growth 

 at their upper extremities. They are usually spherical or ovoidal 

 in form and occur singly or in series of from 2 to 10. The contents 

 of each oogonium become rounded off, forming a single oosphere 

 1 Vide Bot. Centralbl. xvi, 1883. 



Fig. 11. The escape of the zoo- 

 gonidium (z) from its zoogonidan- 

 gium. A, (Edogonium Boscii (Le 

 Cl.) Wittr., from near Senens, Corn- 

 wall. B, (E. Hirnii Gutw., from 

 Churchill, Donegal, Ireland ( x 460). 



