CONFERVOIDE&. 



55 



antheridia are produced by a single cell, or a group of cells, in a 

 filament, dividing several times without increasing in size. Two 

 egg-shaped spermatozoids, each with 2 cilia (Fig. 53 D), are 

 formed in each antheridium, and escape through an aperture in 

 the side ; in the first stages they are enclosed in a bladder-like 

 membrane (Fig. 

 53 B, C). Other 

 cells of the fila- 

 ment swell out 

 and form oogonia 

 (Fig. 53-4), which 

 resemble those 

 of CEdogonium. 

 After fertilisa- 

 tion, the oospore 

 surrounds itself 

 with a thick wall, 

 and assumes a 

 reddish colour. 

 The germination 

 is unknown. 

 The unfertilised 

 oospheres remain 

 green, divide often 

 into 2-4 daughter- 

 cells, and grow 

 into new fila- 

 ments. 



This order, 

 which 'only in- 

 cludes one genus, Cylindrocapsa, forms the connecting link be- 

 tween Ulothricacece and (Edogoniacece. The few species (4) occur 

 only in fresh water. 



Order 6. CEdogoniaceae. The thallus consists of branched 

 (Bulbochcete) or unbranched (CEdogonium) filaments, attached in 

 the early stages. The cells may be longer or shorter, and have 

 one nucleus. Asexual reproduction by zoospores, which have a 

 chaplet of cilia round the base of the colourless end (Fig. 6 a). 

 Sexual reproduction takes place by oogamous fertilisation. On 

 the germination of the oospore, 4 zoospores are formed (Fig. 54 F). 

 They occur only in fresh or slightly brackish water. The division 



A 



D 



FIG. SS.Cylindroeapsainvoluta. A Oogonium withoosphpre 

 (o) surrounded by spermatozoids (s). B Two antheridia, each 

 with two sperraatozoids. C Spermatozoids surrounded by 

 their bladder-like membrane. D Free spermatozoid. 



