HOW TO KNOW THE FRESH-WATER ALGAE 



voir; chloroplasts 1 to several, usually with a conspicuous pyrenoid 



(starch-storing granule); iodine test for starch positive 



Green Algae CHLOROPHYTA 



5 Chromatophores light olive-brown to dark brown; nearly all marine, 

 essentially filamentous, but occurring mostly as thalli of macro- 

 scopic size (brown sea weeds); stored food in the form of laminarin 



and alcohol; starch test with iodine negative 



Brown Algae . .PHAEOPHYTA 



5 Plants marine or fresh-water, but not occurring as brown thalli of 

 macroscopic size 6 



6 Chromatophores yellow-green to yellow- or golden-brown; food in 

 the form of leucosin or oil; starch test with iodine negative; plants 

 unicellular, colonial or filamentous; sometimes swimming with 

 apically attached flagella; many forms (especially the diatoms, 



see Figs. 328-337) with the cell wall impregnated with silicon 



Yellow-green Algae CHRYSOPHYTA 



6 Chromatophores not yellow-green or pale green, but dark golden 

 brown, gray-green, violet-green; food in the form of oil or starch- 

 like carbohydrates; iodire test for starch mostly negative 7 



7 Unicellular, with dark, golden-brown chromatophores; swimming by 

 means of 2 laterally attached flagella; a conspicuous eye-spot usu- 

 ally present; many forms with the cell wall composed of polygonal 

 plates Dinoflagellates PYRRHOPHYTA 



7 Organisms unicellular or filamentous, not swimming by means of 

 laterally attached flagella; chromatophores brown, green, bluish, 

 violet-green or gray-green 8 



8 Chromatophores violet or gray-green, sometimes bluish-green in 

 fresh water, red in marine forms; occurring as filamentous thalli of 

 both macroscopic and microscopic size; food stored in the form of 



starch-like carbohydrates; starch test with iodine negative 



Red Algae RHODOPHYTA 



8 Chromatophores one or two golden-brown (rarely blue) bodies; or- 

 ganisms unicellular; swimming by means of sub-apically attached 

 flagella; food reserve in the form of starch-like carbohydrates; iodine 

 test positive in some CRYPTOPHYTA 



(This class of the algae has several characteristics in common with 

 Dinoflagellates and in some systems of classification is included under 

 the Pyrrhophyta.) 



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