Apparently usually aquatic, these plants are currently growing in damp sand at water’s edge of central lake.
(The western Kaihoka Lake is split in two by a sand bar due to the low water level)
Aquatic plant found on egg of lake
Aquatic rooted in mud in 50 cm of water. Leaves linear
Flipped through Aquatic Plants of MA with no great matches. Stems growing from central area, leaves robust, entire margins, flat (similar to U. intermedia but it's not that species).
Found in a vernal pool in a cedar stand
Violet-black cells in gelatinous sheaths at the surface of a layer of gelatinous cyanobacteria, growing on a lost sock in the mud of a flooded abandoned limestone quarry. I'm not certain that these photos are all of the same organism - some are dark violet and some are more strongly just black. The violet capsule absorbs so much light that it is difficult to induce autofluorescence in the chlorophyll of the cell inside. The first picture shows the violet layer beside some Trentepohlia. The various pictures demonstrate the colours in contrast to some of the other species present (Hassallia, Trentepohlia). Cells themselves are 3-6 µm and the capsules are 6-12 µm. The surface violet-black layer covers a deep layer of gelatinous cells inside lamellated mucilaginous sheaths, of different generations, that I now think are another species entirely.
Part of a gelatinous community: https://inaturalist.ca/observations/208411876.