BROWN* ALGAE 



J»5 



oogonium 



(Fig. 288, A, B. st.). In Sarcophycus, however, the stalk is 

 branched, and a succession of oogonia may be produced, as is seen in the 

 antheridia of Fucus. On the other hand, the antheridial hair of Fucus rr 

 start precisely in the same way as the oogonium, the terminal cell forming the 

 first antheridium. But the growth does not stop there : the stalk-cell shoots 

 out laterally and produces another antheridium, and the process may be con- 

 tinued with irregular sympodial repetition (Fig 287, I.). This finds its biologi- 



fi k 



Fucus 1, group of antheridia. 2. part of an anthendium showing developed 

 spennatozoidsT 3, spermatozoid ; - spot; * -and isolated antheridia 



liberating spermatozoids. 5, ovum surrounded by spermatozoids. 6. secuon tnrougn 

 a fertihsed egg ; ek = nucleus of egg ; spk = nucleus of sperm ; sp = s ^"°**f: 

 (1, 4, 5 after Thuret ; 2, 3 after Guignard ; 6 after Farmer.) (From Stra^burger.) 



cal explanation in the need for a continued supply of numerous spermatozoids, 

 so as to secure fertilisation over a prolonged period. The large number is 

 further ensured bv the divisions m each cell being continued to 64. 



The sohtarv ooeonia. with their few ova, find their biological elucidation 

 in the facts that the ova are large and have a strong chemotactic influence 

 on the motile spermatozoids. Their s e? a high decree of certa 



of successful germination if once fertilised. Their attractive influence secures 

 a hieh probability of fertilisation, notwithstanding their immobility, which 

 has followed on increase in size. But Fucus is not the last term of the series 

 of reduction of the oogonium. In Ascophyllum only four ova are matured in 



