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IOWA ACADEMY OF SCIENCE 
Sporoderm punctate or granulate. 
Cells 10-36 u in diameter Z. stellium 
Cells 35-50 u in diameter Z. cruciatum 
Zygospore between the conjugating cells Z. pectinatum 
102. Z. insigne Kuetz. 
Iowa City. Hobby. 
Ames. Bessey. 
103. Z stellinum Ag. 
Eagle Grove. Floating in Hewitt’s Pond. Buchanan. 
10 U. Z. cruciatum Ag. 
Iowa City. Hobby. 
Eagle Grove. Hewitt’s Pond. Buchanan. 
105. Z pectinatum Ag. 
Iowa City. Hobby. 
2. Spirogyra. 
KEY TO THE SPECIES OF SPIROGYRA. 
Septa between cells smooth, not folded back or replicate. 
Fruiting cells little or not at all swollen. 
One spiral in each cell. 
Zygospores spherical. 
Vegetative cells 30-48 u wide S. porticalis 
Vegetative cells 30-32 u wide S. porticalis alpina 
Zygospore oval to elliptical. 
Broad oval, IV 2 - 2 V 2 times as long as wide. 
18-28 u in diameter S. longata 
33-38 u in diameter S. varians 
Elliptical, 2-3 times as long as wide, 19-23 u in diameter . 
S. communis 
Two or more spirals in each cell. 
Zygospore ovoid or ellipsoid. 
Vegetative filaments 33-40 u in diameter. 
Cells 2-4 times as long as wide S. decimina 
Cells 4-10 times as long as wide S. rivularis 
Vegetative cells more than 50 u in width. 
Cells 54-78 u in diameter S. nitida 
Cells 86-110 u in diameter. 
Cells l%-2 times as long as wide S. jugalis 
Cells V 2 -I times as long as wide S. setiformis 
Zygospore lens shaped or flattened . 
Vegetative filaments 54-62 u in diameter S. majuscula 
Vegetative filaments 70-160 u in diameter. 
Zygospores 102-115 u in diameter S. maxima 
Zygospores 144-15 u in diameter S. crassa 
Fruiting cells distinctly swollen. 
One spiral in each cell S. intermedia 
More than one spiral in each cell. 
Two spirals. 
Dense, close 3-4 turns S. adnata 
Looser, 2-3 turns S. dubia 
Four spirals. Cells 35-40 u wide * S. fluviatilis 
