Isoetes lacustris L.
Coefficient of Conservatism: 9
Coefficient of Wetness: -5
Wetness Index: OBL
Physiognomy: Nt Fern Al

Isoetes lacustris megaspores, distal D. M. Britton megaspores, distal

A widespread species of soft, cold water lakes in nutrient poor, acidic, sandy or gravelly bottoms, usually with little or no associated plant growth. Unlike I. echinospora, almost always growing in deep, cold water (to 6 m).

The leaves are stiffly arching to erect and dark green (sometimes almost black) or reddish-green. Being a polyploid species (2n = 110), the megaspores are large (0.6–0.9 mm in diameter) with a distinct pattern of high ridges that sometimes are anastomosing, but are not fully joined into a network. North American plants ,with typically taller, recurved leaves and more coarsely ornamented, larger megaspores, were long considered distinct from their northern European counterpart as I. macrospora Durieu, but the distinction between these populations is not clear. A single collection from Clark Lake, Gogebic Co., has been determined as I. macrospora forma hieroglyphica N. Pfeiff.


Alger County
Baraga County
Cass County
Cheboygan County
Chippewa County
    Including Drummond Island
Gogebic County
Houghton County
Iron County
Keweenaw County
    Only on Isle Royale
Lake County
Luce County
Marquette County
Ontonagon County
Osceola County
Wexford County


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. August 13, 2022.