Chara brittonii is a very rare charophyte known, on a global basis, from just six localities in the United States; one in New Jersey, one in Ohio, two in Michigan and two in Indiana. Chara brittonii is distinguished by being one of only two North American Chara species that is entirely ecorticate. The species was originally described by T. F. Allen in 1888 based on the holotype specimen which was collected by N. L. Britton from a small pond in new Jersey in 1887. Although Wood relegated the species to a variety of Chara zeylanica, recent molecular data supports maintaining specific status for Chara brittonii. Morphologically the species is distinguished by having sejoined gametangia, eight shield cells on the antheridium, and two tiers of stipulodes. In the summer of 2001 two new populations of Chara brittonii were discovered in intradunal ponds at the Indiana Dunes National Lakeshore while carrying out a submersed aquatic plant survey. These sand-bottom ponds are characterized as ephemeral pannes of higher pH that exhibit extensive drawdown during the summer months. Chara brittonii grows at the water-air interface and often survives as an emergent stranded along shorelines. With a stature seldom exceeding two cm.in height Chara brittonii has an overall appearance more closely resembling that of a moss than that of a charophyte. Associated species at the new Indiana localities include Chara zeylanica,Chara vulgaris, Potamogeton illinoensis and Utricularia cornuta. Factors governing the distribution of Chara brittonii are a circum-neutral to slightly alkaline pH, the presence of quiet undisturbed shorelines, and the possible absence of herbivores such as amphipods.

Key words: Chara brittonii, charophyte, ecology, rare