THE GREEN ALGAE OF NORTH AMERICA 149 



6. CHARACITM A. Braun in Kiitzing, 1849, p. 208. 



Cells with cup-shaped chromatophore and one pyrenoid, from 

 narrowly lanceolate or subcylindrical to broadly ellipsoid or 

 subglobose, often more or less bent, attached by a pointed end 

 or by a stipe-like prolongation to the substratum ; asexual repro- 

 duction by biciliate zoospores of two sizes, escaping by a hole 

 or slit in the cell, also by akinetes ; the occurrence of gametes 

 is doubtful. 



A genus of many species differing much in size and propor- 

 tions of the cell, attached to larger fresh water algae or other 

 objects; common, but easily overlooked. Borzi, 1895 has re- 

 moved a number of species, forming a new genus, Characiopsts, 

 allied to the Confervaceae ; some of the species remaining in 

 Characium are imperfectly known, and may, when more fully 

 studied, also require removal. 



KEY TO THE SPECIES OF CHARACIUM. 



I. Growing on animals. 2. 



i. Not on animals. 3. 



2. Ovoid or broadly ellipsoid. 8. C. De Baryanum. 



2. Elongate. n. 



3. Sessile. i. C. sessile. 



3. With longer or shorter stipe. 4. 



4. Stipe with distinct basal disk. u. C. Pringsheimii. 



4. Stipe without distinct basal disk. 5. 



5. Obtuse. 6. 



5. Acute. 10. 



6. Globose to broadly ellipsoid. 7. 



6. Lanceolate to ellipsoid. 8. 

 7. Having a rounded stopper-like body at apex of cell. 



6. C. obtusum. 



7. Without such body. 5. C. heteromorphum. 



8. Narrowly lanceolate to linear. 4. C. strict um. 



8. Ellipsoid. 9- 



9. Stipe about 4 A* long. 3- C. Naegehi. 



9. Stipe extremely short. 2. C. Sieboldii. 



10. Diam. 15 M or more. 9- C. acuminatum. 



10. Diam. 8 M or less. 7- C. ambiguum. 



ii. With slender prolonged summit. 12. C. gracilipes. 



ii. With blunt summit. 10. C. cylindricum. 



i. C. SESSILE Hermann, 1863, p. 26, PI. VII, fig. 6 ; Wolle, 

 1887, p. 177, PI. CLIX, fig. i. Cells 7-9 A* diam., at first 

 globose, later developing a small apiculum, but continuing 

 sessile. N. J. . Europe. 



