114 Plant Biology 



tion between them. In addition to the green chlorophyll,, there is a blue 

 pigment called phycocyanin (fi ko -si' anin) (Gr, phykos, alga or sea- 

 weed; kyanos, blue). Sometimes a red pigment may also be present in 

 certain species. The chlorophyll is distributed throughout the cell and 

 is not localized in definite bodies known as plastids, as found in other 

 algae (Fig. 29). There is ?io definite organized nucleus; the nuclear, 

 chromatin materials are scattered throughout the center of the cell. The 

 cells are often surrounded by a slimy , gelatinous sheath. Because of this, 

 the term Myxophyta (myx-of'ita) (Gr. myxo, slime; phyta, plants) 

 has been used as the name of the phylum. Foods are stored as glycogen 

 (gli' ko jeii) (Gr. glykys, sweet) , a starchlike carbohydrate. 



Reproduction occurs asexually by fission (cell division). No sexual 

 reproduction is thought to occur in blue-green algae as it does in certain 

 species of other algae. None of the vegetative (body) cells, or reproduc- 

 tive cells, possess threadlike flagella which are present in certain types 

 of algae of other phyla. 



Most species of blue-green algae grow in fresh water, although a few 

 species grow in salt water. They may cause the water in ponds and 

 lakes to have a yellowish-green color and may be so abundant that they 

 are known as ''water blooms," thereby giving the water a "soupy" appear- 

 ance, a "fishy" taste, and a foul odor. Many species occur in soils, on 

 moist rocks, in greenhouses, on flower pots, and in other moist places. 

 Several species grow in hot springs where the temperature may be over 

 75° G. and where they may precipitate the magnesium and calcium salts 

 to form travertine (trav' er tin), a whitish, chalklike deposit which may 

 have bright colors because of the contained algae. Blue-green algae may 

 precipitate calcium carbonate in lake waters to form deposits of marl 

 (L. marga, marl) , an earthy mixture of clay and calcium carbonate which 

 is used as a fertilizer on lime-deficient soils. 



Certain species may be associated with certain species of chlorophyll- 

 less fungi to form plants known as lichens (li'ken) (Fig. 327). A few 

 species may be parasites in the digestive tracts of animals, including 

 man. Blue-green algae, together with other algae and animals, are great 

 sources of foods for aquatic animals. Some species may even be present 

 on other plants as epiphytes (ep'ifite) (Gr. epi, upon; phyta, plants). 

 There are approximately 1,400 species. 



Examples: Gleocapsa (Fig. 29), Oscillatoria (Fig. 29), Nostoc (Fig. 

 29), and Anabena (Fig. 29). 



2. Phylum Chlorophyta (klor -of i ta) (Gr. chloros, green; phyta, 

 plants). — In certain species of green algae the chlorophyll may be asso- 



