WISCONSIN PHYTOPLANKTON 145 



obes. Cells ovoid to elongate-ovoid, with 1-4 parietal, disciform chloro- 

 plasts, each with a single pyrenoid. Old mother cell wall frequently 

 enclosing young coenobia for some time. (Facultative Planktont). 

 Cells 4-7 p broad, 5-10 p. long. 



Bear (2) (rr), Beaverdam (rr), Big (rrr), Birch Island (rrr), Devils (1) 

 (r), Fowler (rrr), Half Moon (rr), Hillman (rr), Kegonsa (rr), Lac Court 

 Qreilles (rr), Lindy (rr), Little Bass (2) (rr), Little Doctor (rr), Mill (rrr), 

 Nancy (rr), Nicaboyne (rr), Okauchee (rrr), Old Taylors (rr), Pine Tree 

 (rr), Sand (1) (rr), Upper Nashotah (rrr), Winnebago (rr). 



CRUCIGENIA IRREGULARIS Wille. PI. 36, Figs. 4-5. 



Biol. Cent. 18: 302. 1898; Nyt. Mag. f. Naturvidensk. 38: 10, pi. 1, fig. 15, 

 1900; W. & G. S. West Trans. & Proc. Bot. Soc. Edinburgh 23: 29, pi. 1, figs. 

 6-7. 1905. 



Coenobia four-celled, with cells in contact at sides and poles, at other 

 times without a definite arrangement. Coenobia irregularly combined 

 into multiple coenobia. Cells ovoid ; with 1-4 parietal, disciform chloro- 

 plasts; with or without pyrenoids. (Facultative Planktont). 



Cells 4-9 fj. broad, 6-14 p. long. Coenobia 8-14 . broad. 15-30 //, long. 



Browns (rr), Camp (rr), Fish (rr), Horseshoe (2) (rr), Mudhen (rr), 

 Reserve (rr), Sand (3) (sss). 



The cell shape is quite similar to that of C. rectangularis but the ar- 

 rangement of cells within the coenobe is very irregular in about half 

 the colonies one meets with. This irregular cellular arrangement coup- 

 led with the larger cell size warrants the separation of the alga from 

 C. rectangularis. The alga is generally reported to be without pyre- 

 noids but I have frequently found them in the chloroplasts of C. irregu- 

 laris. 



CRUCIGENIA CRUCIFERA (Wolle) Collins. PI. 36, Fig. 6. 



Tufts, coll. studies 2: 170. 1909. 



Staurogenia crucifera Wolle, Bull. Torr. Bot. Cl. 6: 140. 1877. 



Staurogenia cruciatum Wolle, Freshw. Algae of U. S. 171, pi. 157, figs. 9-11. 

 1887. 



Coenobia four-celled, rhomboidal, with rounded ends, slightly con- 

 cave sides, and a small rectangular open space at the center. Cells 

 elongate, outer face concave, inner and those in contact with other cells 

 straight. Chloroplast single, parietal, laminate; without a pyrenoid. 

 (Facultative Planktont). 



Cells 3.5-5 p. broad, 5-7 p. long. Coenobia 9-11 p. broad, 14-16 p. long. 



Hillman (rr), Tenderfoot (rr). 



The arrangement of the individual coenobia into compound coenobi* 

 is generally that which Wolle gives in his figure 9 of Staurogenia cruci- 



10 



