146 



WISCONSIN PHTTOPLANKTON 



atum. CoUin's surmise that the reported cruciform marking of the 

 cell wall is probably due to a division of the cell contents is correct and 

 what Wolle calls the cell is in reality the coenobe. The remains of the 

 old cell walls play an important part in binding together the various 

 coenobia of the multiple coenobe. 



Crucigenia truncate sp. nov. PI. 36, Figs. 7-9. 



Coenobe four-celled, with a small rectangular space at the center and 

 held in compound coenobia of indefinite size by the remains of old 

 mother cell walls. Cells quadrately arranged with bases and middle 

 third of inner sides in mutual contact but with apices and outer faces 

 free. Cells elongate, ovoid, with free ends truncate. Cell wall at free 

 apex thicker than in other parts. Chloroplasts 1-4, parietal, disci- 

 form, without pyrenoids. (Euplanktont). 



Cells 4-6 p. broad, 6-10 /* long. Coenobia 6-12 p broad, 12-20 

 H long. Compound coenobia up to 50x75 p.. 



Chain (rr), Hillman (rr), Pine Tree (rr), Travis (rr). 



The species is differentiated by its flattened cell apices and the thicker 

 walls at the apices. The cells are always regularly arranged within the 

 coenobe, but when in compound coenobia the arrangement is frequently 

 irregular. 



CRUCIGENIA APICULATA (Lemmermann) Schmidle. PI. 37, Fig. 1. 



Allg. Bot. Zeitschr. 6: 234. 1900. 



Staurogenia apiculata Lemmermann, Bot. Cent. 76: 151. 1898; For- 

 Bchungsbr. a. d. Biol. Stat. zu Plon 7: 119, pi. 1, fig. 14. 1899; Snow, Bull. 

 U. S. Fish Comm. 22: 376, pi. 1, figs. V^V 9 . 1903. 



Tetrastrum apiculatum (Lemmermann) Brunnthaler, in Pascher, Siisswas- 

 serfl. Deutschl., cistern u. d. Schw. 5 2 : 177, fig. 258. 1915; G. M. Smith, Bull. 

 Torr. Bot. Cl. 43: 472, pi. 24, fig. 3. 1916. 



Coenobia four-celled, embedded in a delicate gelatinous sheath. Cells 

 quadrately arranged with their long axes parallel and a small rectangu- 

 lar space at the center. Coenobia generally in multiple coenobia which, 

 when containing large numbers of coenobia, are frequently irregular. 

 Cells ovoid to triangular, with a short conical projection at the free 

 apex and frequently another one at the side of the base away from the 

 center of the coenobe. Each cell containing 1-4 parietal disciform 

 chloroplasts with one pyrenoid. (Euplanktont). 



Cells 3-7 fj, broad, 5-10 /* long. Coenobia 6-12.5 /* broad, 9-18 

 fi long. Compound coenobia up to 150 p broad. 



Mendota (rrr), Palmer (rrr), South Crab (rr). 



The cells of 16-celled multiple coenobia are regularly arranged but 

 when multiple coenobia contain 150-200 cells the arrangement is fre- 



