THE FRESH-WATER ALGAE 



13s 



5 (11) Cells cylindrical, with no constriction, or at most a very shallow and 



broad constriction, giving a sUghtly undulating outline. 6 



6 (7) 8) Cells not longer than broad, sometimes with a very shallow, broad 



constriction; chromatophore central, with 6 to 10 rays about 

 a pyrenoid Hyalotheca Ehrenberg. 



Filaments long, often twisted, and slippery to the touch. 

 The different diameters of the cells nearly equal, varying 

 from 20 to 35 ju. llie median constriction often very slight. 

 Chromatophore in each cell-half of radiating plates placed 

 about a pyrenoid. 



A broad gelatinous envelop is always present but it is in- 

 visible without reagents. 



Hyalotheca is frequent among filamentous forms of the 

 Conjugales. 



Fig. 107. Hyalotheca dissUiens Br6bisson. a. side view. b. end 

 view. X 575. (Original.) 



7 (6, 8) Cells but little longer than broad, attenuated at the end. 



Leptozosma Turner. 



Filaments long, cateniform; not twisted, or 

 but slightly so. Joints united by a strongly 

 marked suture; near to Bambuscina Kutzing, 

 but differing therefrom in the suture. 



Fig. 108. Leptozosma catenulata Turner. X 300. 

 (After Turner.) 



8 (6, 7) Cells much longer than broad 9 



g (10) Chromatophore a central plate containing a row of pyrenoids. 



Gonatozygon de Bary, 



Length of cells icrato 200M; breadth loto 20M, 

 much like a cell of Mougeotia except that the 

 membrane is covered with minute projections; 

 Fig. 109. Gonatozygon ral/sii de Bary. cells sometimes shghtlv swollen at the ends. 



X about 230. (After de Bary.) 



10 (9) Chromatophores consisting of several parietal spiral bands. 



Genicularia de Bary. 



Diameter of cells 17 to 22.5 /*; length 

 10 to 20 times as great. Membrane cov- 

 ered with fine projections as in Gonatozygon. 

 Fig. no. Genkularia spiroiaenia Bnbisson. X 265. Spiral chromatophores with many pyrenoids. 

 (After de Bary.) 



11 (s) CeUs not cyhndrical 12 



12 (19) End view of cells circular, oval, or elliptical, rarely triangular. . 13 



13 (16) Cells not deeply constricted at the middle r4 



14 (is) Cells cask-shaped, placed end to end, with a shallow narrow con- 



striction at the middle; end view circular, with two oppcK 

 sitely placed projections Gymnozyga. 



The membrane frequently shows longitudinal stripes. 

 Chromatophores in each ceU-half composed of a number 

 of radially-placed plates arranged about a pyrenoid at 

 the center. 



Fig. III. Gymfwzyga 6f ^womi Nordstedt. X s68. (Original.) 



