164 Pla?it Biology 



None of the sexual or asexual reproductive cells bear flagella which is 

 characteristic of red algae. In sexual reproduction the nonmotile male 

 gamete is carried by the water to the female carpogonium (karpo- 

 go' ni um) (Gr. karpos, fruit; gonos, offspring). The latter is character- 

 istic of red algae. Fertilization results in the production of a zygote. 

 Many red algae alternate between a free-living sporophyte and a free- 

 living gametophyte. About 2,500 species are classified in 400 genera. 

 The following typical species will be considered: Nemalion and Poly- 

 si pho7ii a. 



Nemalion (nem -al' i on) (Gr. nema, thread). — This cylindrical, 

 forked, marine, red alga is attached to rocks on the seacoast. The body 

 is composed of interwoven, branched threads surrounded by a gelatinous 

 material (Fig. 63). Some branches bear brushlike filaments whose tips 

 are divided into short antheridia, each containing one sperm. The tips 

 of other branches bear female structures consisting of an enlarged, basal 

 carpogonium (kar po -go' ni um) (Gr. karpos, fruit; gonos, offspring) 

 with an egg and an elongated, hairlike, tubular trichogyne (trik'ojin) 

 (Gr. thrix, hair; gyne, female) to receive the nonmotile sperm. The nu- 

 cleus of the sperm descends the trichogyne to the carpogonium where it 

 fuses with the ^gg nucleus to produce a zygote. Short projections are de- 

 veloped from the carpogonium which grow into short filaments at whose 

 tips are produced the asexual, nonmotile carpospores (kar' po spor) (Gr. 

 karpos, fruit; spora, spore) . The latter germinate to form a new Nemal- 

 ion plant. 



Polysiphonia (poli si -fo' ni a) (Gr. polys, many; siphon, tube). — This 

 marine, red alga grows on rocks and is profusely branched. The main 

 axis and the larger branches consist of a central core made of a single 

 row of elongated core cells surrounded by a layer of jacket cells (Fig. 33) . 

 The elongated cells are connected with each other by cytoplasmic con- 

 nectives which form tubelike structures or ''siphons" ; hence the name 

 Polysiphonia. Each cell has a nucleus and numerous red plastids con- 

 taining phycoerythrin (fi kd e -rith' rin) (Gr. phykos, alga or seaweed; 

 erythros, red) which masks the chlorophyll. Stored foods are insoluble 

 "starch." 



Polysiphonia is diecious (di-e'sius) (Gr. dis, two; oikos, house), the 

 male gametes being produced by one plant and the female gametes by 

 another plant. The lateral branches of the male plants bear clusters of 

 antheridia which produce numerous, nonmotile sperm^ (gametes). On 

 the side branches of other plants are borne female structures known as 



