Fig. 159.
Coleochæte soluta; at left branch bearing oogonium (oog); antheridia (ant); egg in oogonium and surrounded by enveloping threads; at center three antheridia open, and one spermatozoid; at right sporocarp, mature egg inside sporocarp wall.
Fig. 160.
Two sporocarps
still surrounded
by thallus.
Thallus finally
decays and sets
sporocarp free.
Fig. 161.
Sporocarp ruptured by growth
of egg to form cell mass.
Cells of this sporophyte
forming zoospores.
Figs. 160, 161. C. scutata.
328. Antheridia.—In C. scutata certain of the cells of the plant divide into four smaller cells, and each one of these becomes an antheridium. In C. soluta the antheridia grow out from the end of terminal cells in the form of short flasks, sometimes four in number or less ([fig. 159]). A single spermatozoid is formed from the contents. It is oval and possesses two long cilia. After swimming around it passes down the tube of the oogonium and fertilizes the egg.
329. Sporocarp.—After the egg is fertilized the cells of the threads near the egg grow up around it and form a firm covering one cell in thickness. This envelope becomes brown and hard, and serves to protect the egg. This is the “fruit” of the coleochæte, and is sometimes called a sporocarp (spore-fruit). The development of the cell mass and the zoospores from the egg has been described above.