100 WISCONSIN PHYTOPLANKTON 



37, Staurastrum americanum (W. & G. S. AVest) G. M. Smith. 



PI. 77, Fig. 2. 



Trans. Wis. Acad. Sei., Arts & Lett. 10: 351. 1922. 



Staurastrum grallatorium var. americanum W. & G. S. West, Trans. Linn. Soc. 

 2nd. Set. Bot. 5: 265, pi. 17, fig. 15. 1896. 



Cells of medium size, length (with processes) about two-thirds the 

 breadth, deeply constricted, sinus widely open and with an acute 

 apex, isthmus very narrow; semicells obsemicircular, with the apex 

 somewhat convex, dorsal margin without ornamentation but with the 

 wall thicker on the dorsal margin than elsewhere ; angles continued 

 in long processes that have subparallel sides, upper and lower mar- 

 gins of processes crenulate. processes subparallel to divergent and 

 with ends minutely trispinate. Vertical view elliptic, with poles 

 continued in hollow processes with undulate sides, body of cell with- 

 out ornamentation. ( Tychoplanktont. ) 



Zygospores unknown. 



Cells 61 fx long with processes, 29 ju, long without processes ; breadth 

 with processes 90 ju,, without processes 26 ju, ; breadth at isthmus 6.5 jjl. 



Clare (rrr). 



Although but two specimens were seen both agreed well with W. & 

 G. S. West's description. The lack of ornamentation on the apex of 

 the semicells and the thickened wall at this point are quite unlike 

 other biradiate species. The shape of the semicells, lack of apical 

 ornamentation and terminal ornamentation of the processes is so un- 

 like that of ;S'. grallatorium Nordstedt that the alga should be con- 

 sidered a distinct species and not a variety of 8. grallatorium. 



38. Staurastrum grallatorium Nordstedt. PI. 77, Figs. 3-5. 



Vidensk. Medd. f. d. naturhist. Foren. i Kiobenhavn 1869: 228, pi. 4, fi.g. 52. 

 1870. 



Cells somewhat under medium size, breadth (with processes) about 

 twice the length, slightly constricted, sinus very widely open and with 

 a rounded indentation of the relatively broad isthmus; semicells nar- 

 rowly campanulate, apex truncate and with a median portion bear- 

 ing three emarginate verrucae and somewhat elevated above the rest 

 of the apex ; body of semicells, except for the verrucae, without orna- 

 mentation; angles continued in long slightly attenuated hollow 

 processes with sharply crenulate upper and lower margins, ends of 

 processes deeply bifurcate, the bifurcations (not spines) being a con- 

 tinuation of the processes and hollow, processes subparallel. Vertical 

 view elliptic, body of semicells relatively small and with the lateral 

 margins greatly rounded, poles continued in long processes with 

 straight or slightly undulate margins, processes terminating in two 

 arms that lie in the same vertical plane, (Tychoplanktont.) 



Zygospores unknown. 



