BROWN SEAWEEDS 



81 



has been noticed that some of the gametes come to rest 

 prior to the others, and 

 exert some sort of attrac- 

 tion, which causes the 

 still active gametes to 

 swarm around them (Fig. 

 27, B), the result being 

 that one of the active 

 gametes fuses with the 

 resting-cell and produces 

 a zygospore, which pro- 

 duces a new plant. In 

 this way, then, we have 

 sexual reproduction, and 

 we may look upon the 

 gamete which comes to 

 rest first as an egg- cell, 

 the others acting as sper- 

 matozoids. It is worthy 

 of note, however, that the 

 gametes can give rise to 

 new plants without con- 

 jugating. Asexual pro- 

 pagation preponderates 

 in Ectocarpus, but it seems 

 probable that the occa- 

 sional sexual process re- 

 sults in increased vigour. 

 The Fucacese are a 

 family of Brown Sea- 

 weeds embracing over 300 species, a few of which have 



already been described; they are most abundant in the 



li 



A 

 Fig. 27. — Ectocarpus stLicuLOSus. 



A, Part of branch with two sporangia 

 (sp.) which produce gametes (z), 

 x 330; B, egg-ce!l (?) at est sur- 

 rounded by a swarm of male-cells ; 

 G, stages of conjugation. D and C 

 x790. 



