Spirogyra sp. nucleus at 1000x magnification. Collected in Freda Haffner Kettlehole State Preserve wetland.
Collected in Kettlehole wetland
Collected in Freda Haffner Kettlehole State Preserve wetland
Algae between the growing liverworts.
Thank you to Joe Metzger @joem50 who kindly ID my observation.
Here is his explanation "You have the same problem here as you did in http://www.inaturalist.org/observations/3704991 This is in the Non-Vascular Plants (Superphylum Thallophyta) with the Mosses, Hornworts, and Liverworts (Phylum Bryophyta) and more specifically with the Liverworts (Class Marchantiopsida). Sorry I can't get you farther but there don't seem to be any reproductive organs showing or I don't recognize them. One thing I did notice in both, you have multiple plant observations. If you didn't catch it, there is at least one species of Moss in the other one and in this one you have little bits of Stonewort which iNaturalist includes in Charophyte Algae (Phylum Charophyta), most likely in the Class Charophyceae, Order Charales and the Family Characeae which only has five Genera. You can see it clearest at the bottom in the center of http://www.inaturalist.org/photos/4301990 and there's a little showing at the top in the center of http://www.inaturalist.org/photos/4301989 and a piece going bottom to top on the left side of http://www.inaturalist.org/photos/4301992"
Nitella sp. at Littoral Plot I
Collected in floating mat, Upper Gar Lake
Collected in floating mats in East Lake Okoboji
The Charophyta are a division of green algae, that includes the closest relatives of the embryophyte plants. In some groups, such as conjugating green algae, flagellate cells do not occur. The latter group does engage in sexual reproduction, and motility does not involve flagella, since they are totally lacking. Flagellate cells in the form of sperm are found in stoneworts (Charales) and Coleochaetales.