52 SEAWEEDS 



or serve as a repellant towards intrusive organisms, or 

 do both things besides discharging other functions is 

 not clear. The liberation of both oospheres and 

 antherozoids takes place on the ebb-tide in the case 

 of those plants that live between tide-marks, probably 

 as a result of relief from pressure. The return of 

 the tide sets all afloat and enables fertilisation to be 

 effected. The round oospheres are many thousand 

 times of greater volume than the antherozoids, and 

 so far as is known are capable of impregnation at any 

 point. Whether this is effected by one or more 

 antherozoids has not been established, and there is a 

 conflict of both observation and analogy on the point. 

 The fertilised zygote becomes encysted within a 

 cellulose membrane, but in the cases observed is 

 capable of germination without the intervention of a 

 period of rest. On germinating the zygote becomes 

 pear-shaped, and the more pointed end is destined to 

 produce the root-portion of the future thallus, while 

 the upper by repeated cell-divisions gives rise to the 

 tissue-system of the thallus. When the young plant 

 is about a millimetre in length a tuft of hairs appears 

 at the apical dimple. Observations of sufficient 

 exactness are wanting of the stages of development 

 that intervene between this one and a later stage at 

 which the young plant hks come to assume a more 

 definite or even characteristic form. 



Besides the fertile conceptacles there occur in many 

 Fucacece others that remain barren. They originate in 

 precisely the same manner as the fertile conceptacles, 

 and various speculations as to their significance have 

 been hazarded. They are termed cryptostomata ; 



