122 A TEXT-BOOK OF BOTANY 
to resemble the swimming spores. However, it fuses with 
another cell of the same kind, and this behavior and the 
result show that it isa gamete. Asa result of this act of 
fertilization an oéspore is formed, as in the case of Ulothrix 
(§ 65). This kind of sexual reproduction is regarded as 
simple because the pairing gametes are alike, and have not 
become distinguished as egg and sperm, as in @dogonium 
(§ 67) and Vaucheria (§ 68). In those plants separate 
names were given to the organs producing eggs (odgonia) 
and those producing sperms (antheridia). In Ulothrix and 
Ectocarpus, on the other hand, no such distinction can be 
made, and hence the organ producing gametes is called a 
gametangium (gamete-case). Of course odgonia and an- 
theridia are gametangia, but the latter name is generally 
used only when the 
gametes are alike. In 
Ectocarpus, therefore, 
many-celled gametan- 
gia are produced (Fig. 
113, B), in addition to 
one - celled sporangia 
(Fig. 113, A). 
This great group of 
brown Alga, of which 
Ectocarpus is here used 
as a representative, 
is distinguished, there- 
fore, by its swimming 
spores and its similar 
gametes. 
Fic. 114.—Fucus: showing a section of the cavity 73. Fucus.—The 
(gqnemotacle) containing, the ses smaller group of brown 
Alge comprises the 
rockweeds (Fucus) and the gulfweeds (Sargassum), the 
former of which may be used to illustrate the group. 
