DESMIDS FLORA OF MICHIGAN 
255 
Cosmariuni Corda. 
Cosmariuin (ibbreviatiun Racib. Inghani County. 
C. abbreuiatiim var. minor West and West. Barry County. 
C. abbreviaium var. planctonicnm West and West. Gogebic County. 
C. amoemtm Bréb. (PI. 1. Fig. 10). This spccies bas been reportcd 
previoiisly from several counties but is noted here because 
specimens from Schoolcraft County showed zygospore forma¬ 
tion. To the M-riter’s knowledge this reproductive structure bas 
iiever been described in tbe literature and thus the description 
is included here. 
Zygospora spberica, memhrana exteriore levi, inenibrnna inte- 
riore depressîoTiibiis profiindis circularibus regulariler aeqtie 
ornafa: zygospora 46 {i. dîain. 
Zvgospore spberical, outer wall sniooth, iniier wall regularly 
and uniformly ornamented by deep circulai- dépréssions; dia- 
meter 46 y.. 
C. amoeniini var. mediolaeve Nordst. Barry (two stations), Cal- 
boun, and Emmct Counties. 
C. angnlare var. octangulare var. nov. (PI. 1. Fig. 6). 
Varietas semicelluUs oclohiteralibus, apicibiis magis cxseriis, 
marginibus siiperioribiis laieralibus paiihüum retusis. Semi- 
celhiîa a vertice visa elliplica, utroque maryine laterali ut in 
specie proitciiones duas aciilas Iiabente. Anguîi ut in specic 
conspiciie incrassati aciiteqiie acnniinati annon. (.elhdu !21.5- 
26 long 19-2i u laf.; isthmus 7-8.7 jj. lat. 
variety with eight-sided semicolls, more exserled apices, and 
slightly reluse uppcr latéral margins. Vertical view elliptic, 
each latéral margin possessing two sbarp projections as in the 
typical. Angles may or may not be consjiicuously thickened 
and sharply pointed as in tbe typical. Cell lengtb 21.5-26 u.; cell 
vvidlh 19-24 g; isthmus 7-8.7 'ft. Calhoun Lake, Calhoun County, 
Michigan. 
Intermediate expressions between tbe typical form and this 
variety bave been shown in illustrations of Prescott (1938) 
and Irénée-Marie (1938) in whicb some of the semicells bave 
three skies in each latéral margin. 
C. annulatum var. elegans Nordst. Delta County. 
C. arciomn var. tatrica Racib. Schoolcraft County. 
C. binum Nordst. Oakland, Presque Isle and Schoolcraft Counties. 
C. biociilatunj var. hians West and West, Gogebic County. 
C. bireine Nordst. Calhoun County. 
C. bireium var. minas Hansgirg. Barry and Roscommon Counties. 
C. botrytis var. subtumidum fa. /renee-.l/arie fa. nob. (PI. 1, 
