peter_schafran's Identifications

This individual was found in mucky organic soil at the edge of a small, spring-fed rivulet, which was running along the outer edge of a graminoid-dominated bog. The last photo is the best habitat shot I have, unfortunately. The small rivulet runs along the base of/somewhat undercuts the bluff, and thus is not super visible in the photo. The plant was collected near where the grassy edge of the bog and the edge of the rivulet meet, more or less directly in front of where the person in the photo is standing.

Ruler units are 0.5 mm.

https://www.inaturalist.org/observations/183415649
Here is an additional observation of the same individual, with more close-up photos of the plant taken in the field.

Plants numerous, but scattered. Growing in sand, silt, and gravel in 0.5 to 1 meter of water.
Leaves 6-10 cm in length.
Megaspores 450--550 μm in diamemter; uniformly echinate, spines thin and sharp, not reduced near the equator; girdle obscure.
Ligule conspicuous, deltoid, >1 mm long.

Note: Isoetes echinospora was previously recorded at Lake Padden by legendary botanist/plant collector Wilhelm Suksdorf in 1890.

Vernal Pool with Isoetes piedmontana at Forty Acre Rock Heritage Preserve (2,267 acres), designated as a National Natural Landmark, at the boundary of the Sandhills and Piedmont regions of South Carolina; this winter ephemeral goes dormant when weather gets hot and water dries up.

Distribution: Scattered shallow pools on of granitic flatrocks in the Piedmont, southern VA to eastern AL.

Abundance: Very rare as a whole across the Piedmont; locally fairly common in Wake-Franklin County area.

Habitat: Spots of (granitic) flatrocks with seepage; all other Isoetes species grow in wetlands or wet places.

Phenology: Fruits from May to October.

Identification: All Isoetes species have numerous very slender, terete (rounded), hollow, grass-like leaves, swollen at the common base, where megaspores are present (the key structure for separation of species).