floating or adherent to a substrate, dark green or brownish; tri- 

 chomes straight or curved, briefly tapered at the apex, which is 

 hooked or spiralled; sheaths sticky, distinct finally but becoming 

 confluent with the mucilage of the plant mass; apical cell capitate, 

 with a rotund or conical calyptra; cells not constricted, 6— 9/x in 

 diameter, 2— 6/x long, granular at the cross walls; cell contents blue- 

 green. 



On mud near stream, Mich. 



LYNGBYA Agardh 1824, p. XXV 



Filamentous, composed of a uniseriate, unbranched trichome of 

 cells inclosed by a non-gelatinous, more or less firm sheath; plank- 

 tonic and solitary, or aggregated, forming entangled masses on 

 substrates or intermingled among other algae; some species spirally 

 coiled; trichomes mostly cylindrical throughout and tapering very 

 slightly, if at all, toward the apices, which are usually not capitate. 



In favorable habitats some of the planktonic species may become 

 superabundant, but unlike Aphanizomenon flos-aquae and Micro- 

 cystis aeruginosa, the plants remain distributed throughout the 

 water and do not form sticky masses and floating scums; hence they 

 seldom figure in water bloom disturbances. 



Key to the Species 



1. Filaments spirally coiled or twisted, sometimes 



entwined about other algae 2 



1. Filaments straight, curved, or entangled, 



but not definitely coiled 5 



2. Filaments wound about and creeping over 



other filamentous algae L. epiphtjtica 



2. Filaments not entwined about other algae 3 



3. Trichomes very loosely spiralled, or merely 



wavy ( often straight ) L. spirulinoides 



3. Trichomes closely coiled and twisted 4 



4. Trichomes irregularly twisted and coiled — L. Lagerheimia 



4. Trichomes regularly spiralled L. contorta 



5. Filaments 20-58m in diameter 6 



5. Filaments less than 20ai in diameter 8 



6. Filaments euplanktonic, 20-24/x in diameter; 



sheath O.S^/x thick; solitary.. L. Birgei 



6. Filaments tychoplanktonic, intermingled with 



other algae, or forming a plant mass 7 



7. Filaments 44-58/n in diameter; sheaths up to 



Bfi thick; intermingled with other algae L. latissima 



7. Filaments 8-24-(28)/:t in diameter; sheaths thinner; usually 



forming entangled plant masses — L. aestuarii 



8. Plants euplanktonic and solitary 9 



8. Plants epiphytic, adherent and forming plant 



masses, or entangled among other algae, tychoplanktonic 12 



[497] 



