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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. 



FIG. 114. Fucus: showing a section of the cavity 73. F U C U S . The 



(conceptacle) containing the sex-organs, in qTna ]l pr rr rniin n f brown 

 this case only oogonia. After THURET. 



Algse comprises the 



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

 former of which may be used to illustrate the group. 



