48 WISCONSIN PHYTOPLANETON 



Cells 260 ju. long ; 240 [x broad at base of semicells, 96 ju, broad at 

 apex of polar lobe; 32.5 fi broad at isthmus. 

 Hill (rrr). 



var. FiMBRiATA (Ralfs) Nordstedt. PI. 62, Fig. 1. 



Vidensk. Medd. f. d. naturhist. Foren. i Kiobenhavn 1888: 190. 1888. W. & G. S. 

 West, Monogr. Brit. Desm. 2: 99, pi. 46, fig. 6; pi. 47, figs. 3-4. 1905. 



Micrasterias fimbriata Ealfs, Brit. Desm. 71, pi. 8, fig. 2. 1848; Wolle, Desm. 

 U. S. 109, pi. 36, figs. 1-6. 1884; Freshw. Algae of U. S. 338. 1887. 



Variety with polar lobes less sharply exserted on account of the 

 narrower polar incisions ; polar lobe with the curved spine within the 

 lateral margin lacking but with the delicate spine on either side of 

 the apical notch. Cell wall smooth. (Tychoplanktont.) 



Zygospores spherical, with scattered rather slender spines that have 

 furcate apices and with the furcate ends recurved; at times with 

 the notch very deep and extending below the middle of the spine 

 (WoUe). 



Cells 293 fi long ; 252 fi broad at base of semicells, 67.5 fi broad at 

 apex of the polar lobe ; 40 fx. broad at the isthmus. 



Clear (rrr). Horseshoe (rrr). 



Ralfs describes both M. apiculata and M, fim1)riata in his British 

 Desmidieae. The two are not considered distinct species since both 

 have the same recurving of polar spines of different length and the 

 same recurving of the spines at the ends of the lateral lobules. The 

 chief difference in cell shape of the two is the exsertion of the polar 

 lobe and the greater inflation of this lobe in M. apiculata. Since 

 M. apicultata was described first it is taken as the type and M. fim- 

 hriata is placed as a variety. The variety spinosa of M. fimbriata does 

 not seem worthy of varietal recognition so is considered a form which 

 differs from M. apiculata var. fimhriuta in the small spines near the 

 lateral and polar incisions. All transitions from this form to the 

 true variety can be found. 



Forma spinosa (Bissett) W. & G. S. West (Monogr. Brit. Desm. 2: 

 100, pi. ^7, fig. 5. 1905). Cells with rows of spines along the median 

 construction, polar and lateral incisions. PI. 61, Fig. 2. (Tycho- 

 planktont.) 



Cells 257 fi long ; 220 fj. broad at base of the semicells, 70 fj. broad 

 at apex of the polar lobe, 39 [i broad at the isthmus. 



Crooked (rrr), 



9. Micrasterias Thomasiana Archer. PI. 60, Fig. 5. 



Quart. Jour. Micr. Sci. N. S. 2: 239, pi. 12, figs. 1-10. 1862; G. S. West, Jour. 

 Linn. Soc. Bot. 34: 384, pi. 9, figs. 6-8. 1899; W. & G. S. West, Monogr. Brit. 

 Desm. 2: 110, pi. 51, figs. 3-6. 1905. 



Cells large, oval in outline, deeply constricted, sinus linear and with 

 outer portion closed, isthmus narrow; semicells five-lobed, lobular 



