CYLINDROSPERMUM Kuetzing 1843, p. 211 

 Filaments straight, curved, or loosely entangled, each surrounded 

 by a soft fikn of mucilage which is confluent with others, forming 

 an expanded mass of indefinite shape on soil or on submerged sub- 

 strates. Heterocysts ovate or ellipsoid, one at either end of the 

 trichome, or at only one end. Cells cylindric or barrel-shaped and 

 constricted at the cross walls. Gonidia ovate, ellipsoid, or sub- 

 cylindric, adjoining the heterocyst, solitary or several in a series 

 with smooth, punctate, or granular calls; inclosed by a thick, close 

 sheath. 



Key to the Species 



1. Gonidia occurring in a series 2 



1. Gonidia solitary, rarely 2 together 3 



2. Cells 4-5/u, in diameter; gonidia 8-10m in diameter C. catenatum 



2. Cells 2. 3-3. 5m in diameter; gonidia 4-5.5|U in diameter C. Marchicum 



3. Gonidia cylindrical or subcylindric - 4 



3. Gonidia ellipsoid or ovate 6 



4. Cells 1.8-2^1 in diameter; gonidia subcylindric, 



3. 5-3. 8m in diameter C. minimum 



4. Cells larger, 3.8-4. 5-(6)m in diameter; gonidia 



cylindrical, or subcylindric o 



5. Gonidia cylindrical, with smooth walls C. stagnale 



5. Gonidia subcyHndric, with roughened, punctate walls C. majus 



6. Gonidia with punctate walls when mature — - 7 



6. Gonidia with smooth walls — 8 



7. Gonidia &-7/x in diameter C. minutum 



7. Gonidia 14.8^ in diameter C. majus 



8. Cells 2-2.5ai in diameter; gonidia 8-9,". in diameter C. minutissimum 



8. Cells and gonidia larger 9 



9. Gonidia 9-12ai in diameter, 1{)-20ai long C. muscicola 



9. Gonidia 12-14/i in diameter, 20-38m long — C. licheniforme 



Ctjlindrospermum catenatum Ralfs 1850, p. 338 

 PI. 122, Figs. 9, 10 



Filaments united by their confluent mucilage to form dark green 

 patches on submerged aquatics or on damp soil. Cells rectangular 

 to short-cylindric; slightly constricted at the cross walls; 4-5fi in 

 diameter, 4-7 [x. long. Heterocysts ovate to ellipsoid, 4-5/^ in diam- 

 eter, 4-7 fi long. Gonidia oblong; formed in a series adjacent to the 

 heterocysts; with a smooth brownish wall when mature; 8-1 0/a in 

 dtameter, 14-18/x long. 



On aquatic vegetation; tychoplanktonic. Mich., Wis. 



Cylindrospermum licheniforme (Bory) Kuetzing 1847, p. 197 



PI. 131, Fig. 14 

 Filaments entangled and forming an expanse of macroscopic 



[529] 



