no Minnesota Algae 



mic. in diameter, not constricted at joints; cells 2-6.4 mic in 

 length L. versicolor 



III Trichomes 5-60 mic. in diameter 



1 Plants living in salt water, epiphytic; plant mass caespitose 



(i) Plant mass purplish-violet; trichomes 5-8 mic. in diameter; con- 

 stricted at joints; cells 2.8-4.6 mic. in length; cell contents rose- 

 colored L. gracilis 



(2) Plant mass dull blue-green; trichomes 6.5-8 mic. in diameter, con- 



stricted at joints; cells 2-4 mic. in length; cell contents pale 

 blue-green L. meneghiniana 



(3) Plant mass dark or dull yellowish green; trichomes 14-31 mic. in 



diameter, evidently constricted at joints; cells 4-10 mic. in 

 length; cell contents frequently showing scattered coarse gran- 

 ules, olive green L. sordida 



2 Plants living in salt water; plant mass caespitose, extended, mucous, 



dull yellowish or dark green, when dried becoming dark violet; 

 sheaths thick 

 (i) Trichomes S-12 mic. in diameter; apex of trichome slightly taper- 

 ing, capitate; cells 2-3 mic. in length L. semiplena 

 (2) Trichomes 9-25 mic. in diameter; apex of trichome not tapering, 

 not capitate; cells 2-4 mic. in length L. confervoides 



3 Plants living in salt, brackish, fresh or warm water or on moist earth 

 (i) Trichomes 8-24 mic. in diameter; apex of trichome slightly taper- 

 ing, capitate; apical cell truncate, rarely somewhat acute-conical; 

 cells 2.7-5.6 mic. in length L. aestuarii 



(2) Trichomes 16-60 mic. in diameter; apex of trichome not tapering, 

 not capitate; apical cell rotund; cells 2-4 mic. in length 



L. majuscula 



4 Plants living in fresh water, often in hot or warm water 

 (i) Plant mass caespitose, dull or dark green or blue-green 



A Sheaths thickened and roughened with age; trichomes 6-10 mic. 

 in diameter, not constricted at joints; apex of trichome not 

 tapering, not capitate; cells 1.7-3.3 mic. in length 



L. martensiana 



B Sheaths colorless, thin, papery; trichomes 7.5-13 mic. in diameter, 

 especially constricted at joints; apex of trichome not tapering, 

 not capitate; cells 3-10 mic. in length L. putealis 



C Sheaths colorless, thick, roughened; trichomes 11-16 mic. in diame- 

 ter, not constricted at joints; apex of trichome slightly taper- 

 ing, somewhat capitate; cells 2-3.4 mic. in length 



L. major 



(2) Plant mass floating, olive green; filaments forming a regular loose 



spiral throughout the whole or a portion of their length; trich- 

 omes 14-16 mic. in diameter, not constricted at joints; cells 3.4- 

 6.8 mic. in length L. spirulinoides 



(3) Plant mass formed of loosely entangled filaments, dark green; 



