118 Plant Biology 



plants) . Depending upon the species, asexual reproduction may occur 

 by fragmentation, by motile zoospores, or by nonmotile spores. Depend- 

 ing upon the species, sexual reproduction may occur by isogamy, by 

 heterogamy, or by oogamy. When present, the motile, pear-shaped re- 

 productive cells bear two lateral flagella of unequal length. 



Certain brown algae are of value as sources of iodine, potassium, 

 fertilizers, and foods for animals and man. There are approximately 900 

 species. 



Examples: The Kelp (Laminaria) (Fig. 32) and Rockeed (Fucus) 

 (Fig. 32). 



Fig. 32. — Brown algae of the phylum Phaeophyta. A, The kelp {Laminaria sp.) ; 



B, the rockweed {Fucus sp.). 



5. Phylum Rhodophyta (ro -dof i ta) (Gr. rhodon, red; phyta, plants) . 

 • — The red algae are frequently referred to as "sea mosses" because of 

 the fancied resemblance of certain forms to true mosses. They contain 

 plastids with chlorophyll associated with a red pigment called phycoe- 

 rythrin (fai ko e -rith' rin) (Gr. phykos, alga or seaweed; erythros, red) 

 and sometimes with a blue pigment called phycocyanin. In most species 

 the plants are multicellular and may be branched or rather simple, in 

 the form of a ribbon cylinder, or sheet. Different species vary in size 

 from a few inches to several feet in length. Each cell contains a nucleus, 

 central vacuoles, and one or several plastids, some of which possess pyre- 

 noids. Broad, cytoplasmic strands which connect adjacent cells are fea- 

 tures of red algae. Stored foods are insoluble ''starches." 



