1910] Fernald and Wiegand,— Juncus effusus 83 
That the American and European material of Juncus effusus is not 
identical seems to have been first noticed by Rostkovius in 1801, but 
apparently his discriminating observation has been overlooked by 
most later authors. He says: “Specimens of this species from North 
America seem to differ a little in color, for the petals even in fruiting 
flowers are green; otherwise the structure of all parts is the same as in 
ours," ! 
In their distribution in North America the varieties of Juncus 
effusus are confined to the regions east of the Great Plains and west 
of the Rocky Mountain System, mostly at comparatively low altitudes, 
being apparently unknown on the Great Plains or in the Rocky Mts. 
In the East they rarely extend westward beyond the region of the 
Great Lakes and the Mississippi Basin except on the southern coastal 
plain. In the West they are unknown east of British Columbia, 
Washington, Oregon and California. ‘This extreme isolation of the 
plants may to some extent account for the fact that we do not find 
identical varieties upon the eastern and western edges of the con- 
tinent. 
The different forms of Juncus effusus in America, as we have identi- 
fied them, may be distinguished as follows: 
A. Flowers small, sepals 1.7-2.6 (rarely 2.9) mm. long, mostly somewhat 
spreading from the base: perianth-segments not very dark but usually 
with two distinet brown lateral bands, rather soft in texture and there- 
fore not rigid when dry: inflorescence small (1-4 em. in diameter), 
or if larger with the sepals less than 2.6 mm. long. 
Culms rather stout, 1.5-4 mm. in diameter at the top of sheaths: 
sheaths pale: inflorescence small, compact. 
Culms finely many-striate and usually deep-green var. compactus. 
Culms coarsely 12—15-suleate, usually pale-green var. conglomeratus. 
Culms rather slender, 1-2 (rarely 3) mm. in diameter at the top of the 
sheaths: sheaths dark: inflorescence small and rather close, 
var. decipiens. 
Culms very slender, 1-1.5 mm. in diameter at the top of the sheaths: 
sheaths pale: inflorescence much more open, loosely fastigiate. 
var. exiguus. 
B. Flowers of medium size, sepals 2.5-2.9 (rarely only 2) mm. long, rarely 
spreading: perianth-segments very dark-brown, mostly soft in texture, 
therefore not rigid when dry, each with two broad dark-brown lateral 
1Specimina huius speciei ex America boreali colore parum differre videntur, sunt 
enim petala etiam in fructiferis floribus viridia; ceterum structura omnium partium 
eadem ac in nostra.— Rostk. Dissert. de Junco, 11 (1801), 
