THE ALGE 233 
of the conceptacles when the plants which bear them 
become partially dry between tides. When the plants 
are again covered with sea-water, each egg becomes sur- 
rounded by actively swimming sperms which set the egg 
itself in motion 
(Fig. 168, B). The 
egg is soon fertil- 
ized, becomes an 
odspore surrounded 
by a special cell- 
wall, germinates, 
and forms a new 
plant. The unlike- 
ness of the male 
and female gametes 
of Fucus in form, 
size, and motile 
power is very great; 
tens of thousands 
of sperms would 
be needed to make 
up a bulk equal to 
that of a single egg. 
299. Summary 
of the Brown Alge. 
— The brown algze 
are practically all 
of them marine, 
Fic. 164. Transverse Section of Conceptacle of a 
Rockweed (Fucus platycarpus). (x about 35.) 
h, hairs; a, antheridia; 0, odgonia. 
abounding most in the northern seas, and are usually 
known as seaweeds. They vary greatly in size, some being 
almost microscopic, while others, like the giant kelps of 
the Pacific, reach a length of from six hundred to nearly 
