Asa Gray, The Manual of the Botany of the Northern United States
“ Sepals and stamens 3–4. Fert. Fl. Sepals 3, oblong, more or less unequal; a rudiment of a stamen commonly before each in the form of a hooded scale. Stigma sessile, pencil-tufted. Achene ovate, compressed, erect, partly or nearly naked.—Stingless, mostly glabrous and low herbs, with opposite leaves and united stipules; the staminate flowers often mixed with the fertile. (Named from the shape of the larger sepal of the fertile flower in the original species, which partly covers the achene, like the pileus, or felt cap, of the Romans.) ”
