264 . COLLEGE BOTANY 



(anther idium and oogonium) containing highly developed ga- 

 metes (sperms and oospores). The Chlorophyceoe can be di- 

 vided into the following orders: 



1. V olvocales — unicellular, single or colonial, usually motile 

 species (page 264). 



2. Protococccdes — unicellular, colonial, non-motile species 

 (page 266). 



3. Confervales — multicellular, simple or branched filaments 

 or flat branched filaments or flat thallus striictures ; reproduction 

 by non-sexual cells or by gametes (page 267).'' 



4. Siphonales — ^usually unicellular but often multinuclear, 

 filamentous species, sometimes branched; reproduction by well- 

 defined organs (page 268). 



5. Conjugales — unicelhilar species or multicellular species ; 

 reproduction by conjugation (page 269). 



6. Oliarales — a group whose place in the plant kingdom is 

 questioned (page 271). 



The order V olvocales is composed of unicellular and colonial 

 forms, which are usually ciliate and motile and therefore have 

 these characters in common Avith one of the groups of lower uni- 

 cellular animals known as Flagellates. Aniong the most com- 

 mon genera are Chlamydomonas, Sphcerella, Pandorina, Eudo- 

 rina and Volvox. 



Clilamydomonas (Fig. 119, a—d) and S^p/icereZZa are unicellu- 

 lar forms which have the power of locO'motion by means of cilia. 

 This power of loco^motion is so highly developed that these 

 species might very readily be mistaken for animals, if it were 

 not for the fact that they contain chlorophyll and perform the 

 same physiological functions as other chlorophyll-bearing 

 plants. Each individual has a red spot known as the '' eye spot," 

 which is supposed to be sensitive to light. This red pigment is 

 sometimes so abundant as to give pools of water a reddish tinge. 

 The so-called " red snow " of the arctic regions is in reality due 

 to masses of algse belonging to this group in which this red 

 pigment is very highly developed. The individual cells eventu- 



