Verbena
2 of the 7 encyclopedias on this shelf carry an entry for Verbena. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a genus of plants of the natural order Verbenacea. The genus consists of numerous species of herbs or shrubs which inhabit the tropical and subtropical parts of the world; most numerous in America, more rare in Asia and Africa. They have opposite leaves, sessile bracteated flowers in simple or panicled spikes, terminal or axillary; a tubular five-toothed calyx, tubular corolla more or less curved with a spreading limb, generally unequally lobed; four stamens, included in the tube, the upper pair sometimes without anthers; a slender style with capitate stigmas. The ripe fruit splits into two or four nutlets, each containing one seed. The genus is more remarkable for the beauty of a number of the species, which under cultivation have given origin to numerous varieties greatly prized for their brilliant colored flowers, than for other virtues, though formerly the English species was credited with potent medicinal qualities, particularly in ailments of the bladder and in the cure of defective vision, which, however, appear to have been purely imaginary. It was also worn on the person as a protection against blasts and to promote general good fortune, for which purpose it was gathered with special observances and ceremony. The lemon-scented verbena is Aloysia citriodora, which belongs to the same natural order; but the perfumers' oil of verbena is derived from the lemon grass. Vol. X 13
Aiton's Encyclopedia (1910)
an annual flowering herb of the vervain family. Botanically the vervain family is near the mints, but the verbenas look more like phloxes, the flowers being only slightly one-sided. Of 110 species all but one are American. A large number of wild verbenas occur in the United States and the Canadian Provinces, some of them quite handsome; others are weedy. Our beautiful garden varieties are from species native to southern Brazil and the La Plata region. It is expected that valuable strains will be obtained from some of our western verbenas. Verbenas are quick growers from seed planted in the open, and give a fine show of color until killed by hard frosts.