''Isoetes riparia'', the shore quillwort, is a species of plant in the family

Isoetaceae Isoetaceae is a family including living quillworts (''Isoetes'') and comparable extinct herbaceous lycopsids (''Tomiostrobus ''Tomiostrobus'' is an extinct quillwort genus from the Early Triassic of Australia, China and Russia, which was espe ...

. It can be found in rivers, creeks, and tidal mud flats in southern

Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...

and southeastern

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central C ...

, south to eastern New York. It has 5 to 35 long, erect bright green to yellow-green leaves, which are 6 to 35 centimeters long. The velum covers one fourth of the sporangium, which can be 7 millimeters long and 4 millimeters wide. The elongated ligule can grow to be 3 millimeters long. The spherical megaspores are 430 to 680 micrometers in diameter with closely set ridges. The kidney-shaped microspores are 24-35 micrometers long, and usually have spine-tipped tubercules. The megaspores can sometimes come to resemble that of either '' I. echinospora'', if the megaspores become eroded and bear projections that could resemble spines, or '' I. macrospora'', if the broken ridges take a certain shape.

References

riparia ''Riparia'' is a genus of passerine birds in the swallow family Hirundinidae. These are small or medium-sized swallows, ranging from in length. They are brown above and mainly white below, and all have a dark breast band. They are closely ass ...

Flora of North America Taxa named by George Engelmann Taxa named by Alexander Braun {{Lycophyte-stub