This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Stems erect, 1°-2 1/2° high, about 1" thick, arising at intervals from a creeping proliferous rootstock about 1 1/2" in diameter; basal leaves reduced to bladeless clasping sheaths; panicle commonly 7"-15" high, spreading, its subtending leaf usually 4'-10' long; perianth 1" in length or a little less, its parts with a green midrib, equal, lanceolate, the outer acute, the inner obtuse; stamens 6, nearly as long as the perianth, the anthers shorter than the filaments; capsule almost twice as long as the perianth, broadly ovoid, conspicuously mucronate, brown and shining, barely dehiscent, 3-celled; seed obliquely obovoid or oblong, somewhat misshapen by compression in the capsule, about 4" long, none with perfect markings seen.
In swamps, mountains of Schuylkill and Lebanon counties, Pennsylvania, and in Florida.
Juncus balticus Willd. Berlin Mag. 3: 298. 1809.
Stems erect, 8-36' high, 1/2"-1 1/4" thick, arising at intervals from a stout creeping rootstock 1"- 1 1/2" thick; basal leaves reduced to bladeless sheaths; panicle commonly l'-2 1/2' high; perianth 1 1/2"-2 1/4" long, its parts lanceolate, acute, or the inner sometimes obtuse, nearly equal, brown with a green midrib and hyaline margins; style 1/2"-1" long; stigmas a little shorter; stamens 6, about two-thirds the length of the perianth; anthers about 3/4" in length, much longer than the filaments; capsule about as long as the perianth, pale to dark brown, narrowly ovoid, conspicuously mucronate, 3-celled; seeds usually with a loose coat, nearly 1/2" long, oblong to narrowly obovoid, oblique, about 40-striate.
On shores, Newfoundland and Labrador to Alaska, Pennsylvania, Missouri and Nebraska; far south in the western mountains. Also in Europe and Asia. Consists of many races.
Juncus Roemerianus Scheele, Linnaea 22: 348. 1849.
Stems 20'-4° tall, erect, arising singly from a tough scaly horizontal rootstock 2 1/2"-5" thick; inner sheaths bearing erect blades of about the same length as the stem; inflorescence 2Y-6' high, diffusely spreading, its leaf 4'-10' long; heads 2-6-flowered; perianth pale brown, i"-i 3/4" long, the parts linear-oblong, the outer acuminate, the inner shorter and bluntly acute; flowers imperfectly dioecious; stamens 6, on fertile plants reduced to sterile staminodia; capsule brown, about as long as the perianth, narrowly obovoid, obtuse or truncate, mucronate, 3-celled; placenta very thick and spongy, about one-third as broad as the valve; seed dark brown, i"-|" long, obovoid, abruptly apiculate, indistinctly reticulate or distinctly 20-26-ribbed and the intervening spaces imperfectly cross-lined.
In brackish marshes, New Jersey( ?), Virginia to Florida and Texas.