THE FRESH-WATER ALGAE I35 



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



broad constriction, giving a slightly 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 Hyalotlieca Ehrenbcrg. 



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

 =-£=::5^==;«==5=^^^^- Thc diffctent diameters of the cells nearly equal, varying 



hi^''''W^I^3^^«^IS- ^''^"^ ^° ^° ^5 ^' ^^^ median constriction often ver>' slight. 



A Chromatophore in each cell-half of radiating plates placed 

 |)it5<»««ti»dks,5j^^]t^- about a pyrenoid. 



!t^t4U«^(^i^»;iiig)[><'j^^^^ A broad gelatinous envelop is always present but it is in- 



visible without reagents. 



Hyalotheca is frequent among filamentous forms of the 

 B Conjugalcs. 



Fig. 107. Hyalotheca dissiliens Brebisson. a. side view. 6. 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 Kiitzing, 

 \rA \3A.^ri^ "^ — ^^^^^ ''^^:=:r:^_i^ ^^^ differing therefrom in the suture. 



'V\s#ss:^ Fig. 108. Leptozosma catenulata Turner. X 300. 



(After Turner.) 



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



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



Gonatozygon de Bary. 



r;^S^^^n^^^S^^^^^^ Length of cells 100 to 200 m; breadth 10 to 20M, 



4,;^^^,^,=,,,,,^,,;^,:^.=-.==*. — -•-:■ ''*~^ ~~"'"°^^^^ much like a cell of Mougeotia except that the 



membrane is covered with minute projections; 

 Fig. 109. Gonatozygon ralfsii de Bary. cells sometimes slightly swollen at the ends. 



X about 230. (After de Bary.) 



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



Genicularia de Bary. 



[ |^V'<pii:g.^?^-^^'^- ^ ^^ Diameter of cells 17 to 22.5 n', length 



i^'^C-;'-^'^?^;;^^^ 10 to 20 times as great. Alembranc cov- 



^?> Ivis-uy *.■.'.■. , :fvs . /i^i ^W ^tiJ^i*! Mi,^ )'S,:^^i^f^ ered with fine projections as in Gotiiitozygon. 



Fig. no. Genicularia spirotaenia 'Rx€b\sson. X 265. Spiral chromatophores with many pyrenoids. 



(After de Bary.) 



11 (5) Cells 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 14 



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



striction at the middle; end view circular, with two oppo- 

 sitely placed projections Gymuozyga. 



The membrane frequently shows longitudinal stripes. 

 iii^ l^Q^if^::::-^ Chromatophores in each cell-half composed of a number 

 ^"^^^^ -"""Vj^!^*) ^^^^r'*^ of radially-placeil plates arranged about a pyrenoid at 

 ^51^: ^}j^^^^^^l^ the center. 



Fig. III. GymnozygabTtbissoniiNoT(\sieAi. X s6"^- (Original.) 



