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IOWA ACADEMY OF SCIENCE 
B. Dioecious species. 
1. Nannandrous (with dwarf males). 
a. Dwarf males unicellular 0. cataractum 
2. Macrandrous. 
a. Oogonia little or not at all swollen O. capillar e 
b. Oogonia manifestly swollen. 
^Diameter female cells 9-12 u 0. franklinianum 
** Diameter female vegetative cell 12-30 u. 
+Diameter oospore 28-35 u 0. pringsheimii 
++ Diameter oospore greater. 
=Diameter male vegetative cells 15-25 u O. cardiacum 
==Diameter male vegetative filaments 14-16 u O. carbonicum 
C. Organs of fructification imperfectly known. 
1. Oospores globose or sub-globose O. fonticolum 
2. Oospores ellipsoid or oval. 
a. Diameter vegetative cells 30-42 u O. giganteum 
b. Diameter vegetative cells 5-6 u O. longatum 
55. O. cryptoporum Wittr. 
Iowa City. Hobby. 
56. O. autumnale Wittr. 
Iowa City. Hobby. 
57. O. fragile Wittr. 
Iowa City. Hobby. 
58. 0. cataractum Wolle. 
A species that has been referred to this species provisionally has been 
found several times in stagnant water. Answers description very well, but 
for the habitat, which Wolle gives as rapids. 
Ames. 1905. Buchanan. 
59. O. capillar e (L.) Kuetz. 
One of the commoner forms. Specimens were often found which were 
referred here, but were not fruiting. 
Iowa City. Hobby. 
Ames. Pond. 1905. Buchanan. 
60. O. franklinianum Wittr. 
Gar Lake, attached to weeds, very abundant. Buchanan. 
61. O. pringsheimii Gram. 
Iowa City. Hobby. 
62. O. cardiacum (Hass.) Kuetz. (0. inequale) . 
Ames. Bessey. 
63. O. carbonicum Wittr. 
Wolle in Fresh Water Algae says: “The only specimens of this species 
identified were from Iowa.” 
Iowa City. Hobby. 
6U. O. fonticolum A. Br. 
Iowa City. Hobby. 
65. O. giganteum Kuetz. 
Iowa City. Hobby. 
66. O. longatum Kuetz. 
Ames. Bessey. 
