is an annual herb occurring in wetlands. Leaves are 3-10cm long,
linear, with tips sharply pointed. Scapes are slender, somewhat
twisting, and grow to 5-30cm in height. Sheaths at the lower parts
are tubular, 3-5cm in length. Flower heads are 3-5cm long, in an
obconical shape; involucral scales, green-white, are somewhat longer
than the flower heads. Male and female flowers are bimerous; sepals
and petals are two in both sexes, and stamens are generally four.
Bloom time: August-September.