Survey of Plant Kingdom 115 



ciated with additional pigments known as carotinoids (carotene and xan- 

 thophyll). The chlorophyll is localized in definite bodies called plastids, 

 or more specifically known as chloroplasts (klo' ro plast) (Gr. chloros, 

 green; plastos, moulded or body) (Fig. 30). The cell wall consists of 

 cellulose (sel'u losz) (L. cellula, little cell)^ and the stored food is starch. 

 The latter is formed by special structures known as pyrenoids (pi' re noid) 

 (Gr. pyreuj fruit-stone; eidos, resemblance) located on the chloro- 

 plasts. The nucleus is well organized^ as is true of all algae except the 

 blue-green. Green algae vary in structure; the plant body may be U7ii- 

 cellular, colonial, or multicellular, depending upon the species. When 

 the vegetative (body) cells or the reproductive cells are motile, each bears 

 two to jour anterior flagella, usually of equal length. 



- Chloroplctrfc 

 -->Vacl€U5 



Protococcus 



—Ch\orop]ait 



-.//ucleus 

 -Pyrenoid 



Spiroqyra 



Ulothrix 



..Pyrenoid 

 -//Ocleus 



^-Chlorop]Qst 



-.Pyrenoid 

 I //ucleas 



Ch\orop]a5b 



Desmids ^ 



Fig. 30. — Green algae of the phylum Chlorophyta. 



Reproduction occurs (a) asexually by cell division, by fragmentation, 

 by motile zoospores, or by nonmotile spores or (b) sexually by isogamy 

 (i -sog' a my) (Gr. isos, equal; gamos, marriage) with the fusion of gam- 

 etes (sex cells) of equal size, by heterogamy (het er -og' a my) (Gr. het- 

 eros, different) with the fusion of gametes of unequal size, or by oogamy 

 (o-og'amy) (Gr. oon, egg) which is a special type of heterogamy in 

 which the female gamete {^g^) is nonmotile. The particular method 

 or methods of reproduction depend upon the species. The structures 



