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 has come to assume a more 
definite or even characteristic form. 
Besides the fertile conceptacles there occur in many 
Fucacee 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 ; 
