152 Plant Biology 



phyta, plants) has been used as the name of the phylum. Foods are 

 stored as glycogen (starchlike carbohydrate). 



Reproduction occurs asexually by transverse fission (simple cell 

 division). None of the reproductive, or vegetative (body), cells possess 

 threadlike fiagella which are present in many other types of algae. 



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

 species are marine. They may cause the water in ponds and lakes to 

 have a greenish-yellow color and may be so abundant that they are known 

 as ''water blooms," thereby giving the water a "soupy" appearance, a foul 

 odor, and a "fishy" taste. Many species also occur in soils, on moist 

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

 species grow in hot springs with temperatures over 75° C, where they 

 precipitate the magnesium and calcium salts to form travertine, which 

 may have bright colors due to the contained algae. Blue-green algae 

 may precipitate calcium carbonate in lake waters to form deposits of 

 marl on the bottom. 



Other species may grow on other plants as epiphytes (ep' if ites) (Gr. 

 epi, upon; phyta, plants), while still other species are associated with 

 certain species of chlorophyll-less fungi to form plants known as lichens 

 {W ken) (Fig. 327). A few species may even be parasitic in the diges- 

 tive tracts of animals, including man. Blue-green algae, together with 

 other algae, are great sources of food for aquatic animals. About 1,400 

 species are classified in 150 genera. The following typical examples will 

 be considered: Gleocapsa, Oscillatoria, Nostoc, and Anahena (Fig. 29). 



Gleocapsa (gle o -kap' sa) (Gr. gloia, glue; kapsa, box). — Simple, 

 primitive, unicellular plants with each cell composed of (1) an outer, 

 bluish-green region due to the diflfused chlorophyll and phycocyanin 

 (blue pigment) and (2) a central region containing scattered chromatin 

 granules (Fig. 29). There is no organized nucleus and no plastids. 

 Numerous unicellular plants may be grouped together and surrounded 

 by a jellylike material. Gleocapsa reproduces by fission (simple cell 

 division) and is common on wet rocks and other damp places. 



Oscillatoria (os i la -to' ri a) (L. oscillare, to swing). — A linear series 

 of Oscillatoria plants are associated to form a colony which is filamentous 

 (Fig. 29). Each individual cell is self-sufficient and hence is considered 

 as a separate plant. The chlorophyll and phycocyanin (blue pigment) 

 are distributed in the outer region of the cell and not in an organized 

 plastid. The chromatin granules occupy the central region and do not 

 form an organized nucleus. Frequently the living filaments may glide 

 back and forth or may oscillate, hence the name Oscillatoria. Reproduc- 



