90 WISCONSIN PHYTOPLANKTON 



28. Staurastrum longiradiatum W. & G. S. West. PI. 74, Figs. 5-11. 



Trans. Linn. Soc. 2nd. Ser. Bot. 5: 267, pi. 17, fig. 23. 1896; G. S. West, Jour. 

 Linn. 8oe. Bot. 39: 28. 1909. 



Staurastrum gracile var. lulbosum G. M. Smitli non W. West, Trans. Wis. 

 Acad. Sci., Arts & Lett. 19: 649. 1918. 



Cells of medium size, breadth (with processes) 1.5-2 times the length, 

 slightly constricted, sinus widely open, isthmus relatively broad ; semi- 

 cells campanulate and with cyathiform bases, apex flattened and orna- 

 mented with emarginate verrucae; angles of semicells continued in 

 long divergent, parallel or slightly convergent processes with gradu- 

 ally attenuated margins, upper margin of processes deeply crenulate, 

 crenulations on lower surface of processes shallow, ends truncate and 

 with four short divergent spines. Vertical view triangular; body of 

 the cell with straight to slightly concave sides, with an intramarginal 

 row of two or three bidenticulate verrucae on each side of the cell; 

 angles continued in long straight processes with undulate to sub- 

 crenulate margins and a single row of simple verrucae down the cen- 

 ter. Vertical view of basal portion of the semicell triangular with the 

 apices flattened and bearing one or two conical verrucae. Chloroplasts 

 with a small axial mass and two laminate lobes running part way into 

 each process; pyrenoid single and central. (Euplanktont.) 



Zygospores unknown. 



Cells 46-96 /A long with processes, 41-49 /a long without processes; 

 breadth with processes 73-108 /x, without processes 20-28 p. ; breadth 

 at isthmus 8.5-10 /x. 



Amieoy (sss), Bear (ss), Beartrap (rrr), Beaverdam (rr), Birch (aaa), Bird 

 (rrr), Blake (r), Big Butternut (ss), Little Butternut (rr), Butternut (aa), 

 Chetae (cc), Chetek (cc), Clietek (ss). Deer (ss), Des Moines (rrr), Duck (s), 

 Dummy (ss). Hooker (rrr). Horse (cc). Horseshoe (ss). Found (r), Granite (r). 

 Grassy (rrr), Lac Court Oreilles (rrr), Lake of the Woods (rr), Little Bass (rr). 

 Long (aa). Lost (rr). Loveless (rr). Big McKenzie (r). Middle McKenzie (rrr), 

 Nicaboyne (rr), Pokegama (ss), Poplar (rrr), Prairie (rr), Eeserve (r), Eice 

 (rrr), Eound (r), St. Croix (rr). Big. St. Germain (r). Sand (r). Shell (rr), 

 Silver (rr). Squirrel (rrr). Trout (rrr), Vermilion (sss). 



This alga has considerable resemblance to S. gracile Ralfs in the 

 shape of the semicells and especially to the variety cyathiforme in the 

 swollen bases of the semicells. In 8. longiradiatum, however, this 

 swollen base is triangular in vertical view while in 8. gracile var. 

 cyathiforme W. & G. S. West it is circular. 



The determination of this species is based upon a comparison of the 

 Wisconsin material with specimens from the plankton of Yan Yean 

 (Australia) in the G. S. West collection. In the figures of the alga 

 published by W. & G. S. West the ratio between length of the semicell 

 and breadth of the swollen basal portion is approximately 1 :1 but in 

 both the Australian and Wisconsin material this ratio is roughly 2 :1. 

 There is also a greater variation in the divergence of the processes than 

 is given in the original description. 



