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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 is a gamete. As a result of this act of 

 fertilization an oospore 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 (Edogonium 

 ( 67) and Vaucheria ( 68). In those plants separate 

 names were given to the organs producing eggs (oogonia) 

 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 oogonia 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 Algae, of which 

 Ectocarpus is here used 

 as a representative, 

 is distinguished, there- 

 fore, by its swimming 

 spores and its similar 

 gametes. 



73. Fucus. The 

 smaller group of brown 

 Algae comprises the 

 rockweeds (Fucus) and the gulf weeds (Sargassum), the 

 former of which may be used to illustrate the group. 



7U- 



FIG. 114. Fucus: showing a section of the cavity 

 (conceptacle) containing the sex-organs, in 

 this case only oogonia. After THURETO 



