WISCONSIN PHYTOPLANKTON 47 



var. ORNATA Nordstedt. PI. 60, Figs. 3-4. 



Vidensk. Medd. f. d. naturhist. Foren. i Kiobenhavn 1869: 223. pi. 2 Ha 11 

 1870. ' ' '^' ' 



Micrasterias Sol var. ornata Nordstedt. W. & G. S. West, Monogr. Brit. Desm. 

 2: 97, pi. 46, figs. 3-4. 1905. 



Cells with the same proportions, degree of incision and undulate 

 nature of incisions as in the type ; portions of lobes adjacent to sinus, 

 polar incisions, and sometimes lateral incisions with a single row of 

 small spines. (Tychoplanktont.) 



CeUs 240-248 fi long ; 240-258 /x broad at base of semieeUs, 32-35 a 

 broad at apex of polar lobe; 25-27.5 fi broad at isthmus. 



Beaverdam (rr), Found (rrr), Lindy (rrr), Nicaboyne (rrr). Sand (rrr). 



The breadth of the incision is frequently much wider than that 

 which Nordstedt gives in his original figure. The form name elegan- 

 tior has been given to those ceDs with more open incisions and nar- 

 rower lobelets by G. S. West (Mem. de la Soc. neuchateloise d. sc. nat. 

 5: 1035, pi. 22, fig. 44. 1914) and Figure 4 shows a Wisconsin 

 specimen which agrees well with his form. 



8. Micrasterias apiculata (Ehrenberg) Meneghini. PI. 61, Fig. 1. 



Linnaea 14: 216. 1840; W. & G. S. West, Monogr. Brit. Desm. 2: 97, pi. 47, figs. 

 1-2. 1905; Carter, Ann, of Bot. 33: 300 (with text fig.). 1919. 



Cells large, length somewhat greater than the breadth, deeply 

 constricted, sinus with apex linear but outer portion somewhat open, 

 isthmus narrow; semicells five-lobed, with incisions forming lobes 

 extending about half way from the periphery to the cell center, polar 

 incision open and acute-angled, lateral incisions narrow and with 

 slightly divergent to convergent sides; polar lobe with lateral mar- 

 gins subparallel at base and then outwardly divergent at apex, polar 

 apex deeply emarginate and polar angles with two fairly long diver- 

 gently curved spines, polar apex with another conspicuous erect 

 inwardly curved spine just within the lateral margin, apex frequently 

 with a more delicate spine on each side of the median notch; lateral 

 lobes usually equal in size and with two series of rather wide inci- 

 sions, the ultimate lobelets terminating in 1-3 conspicuous outwardly 

 curved spines. Cell wall covered with short spines that point towards 

 the periphery of the cell and which are regularly arranged near the 

 incisions but irregularly arranged in the median portion of the lobes ; 

 region just above the isthmus with 3-5 (usually four and quadrately 

 arranged) more conspicuous spines. Vertical view rhomboid-elliptic, 

 with acute poles. Lateral view of semicells narrowly truncate- 

 pyramidate. Chloroplasts completely fiUing the semicells, with apex 

 of portion in the polar lobe deeply incised, with two prominent ridges 

 extending from the nucleus to the apex of the polar lobe and with 



— „ ^."" — ^ ^^^^y.y^^ CV7 v±±^^ ajjcA ui. Liic puiar jLuue ana wiin 



secondary ridges near each incision of the lateral lobes; about 30 ^VV^/ 

 pyrenoids m each chloroplast. (Tychoplanktont.) .. '• ^^'^h.i 



Zygospores unknown. /- »"'<3^ 





