=930. Genus.=—Yet if we study all parts of the plant, the perennial rootstock, the annual shoot, and the parts of the flower, we find a great resemblance. In this respect we find that there are several species which possess the same general characters. In other words, there is a relationship between these different species, a relationship which includes more than the individuals of one kind. It includes several kinds. Obviously, then, this is a relationship with broader limits, and of a higher grade, than that of the individuals of a species. The grade next higher than species we call _genus_. Trillium, then, is a genus. Briefly the characters of the genus trillium are as follows: [Illustration: Fig. 495. Trillium erectum (purple form), two plants from one rootstock.] =931. Genus trillium.=—Perianth of six parts: sepals 3, herbaceous, persistent; petals colored. Stamens 6 (in two whorls), anthers opening inward. Ovary 3-loculed, 3-6-angled; stigmas 3, slender, spreading. Herbs with a stout perennial rootstock, with fleshy, scale-like leaves, from which the low annual shoot arises, bearing a terminal flower and 3 large netted-veined leaves in a whorl. _Note._—In speaking of the genus the present usage is to say trillium, but two words are usually employed in speaking of the species, as Trillium grandiflorum, T. erectum, etc. =932. Genus erythronium.=—The yellow adder-tongue, or dogtooth violet (Erythronium americanum), shown in fig. 496, is quite different from any species of trillium. It differs more from any of the species of trillium than they do from each other. The perianth is of six parts, light yellow, often spotted near the base. Stamens are 6. The ovary is obovate, tapering at the base, 3-valved, seeds rather numerous, and the style is elongated. The flower stem, or scape, arises from a scaly bulb deep in the soil, and is sheathed by two elliptical-lanceolate, mottled leaves. The smaller plants have no flower and but one leaf, while the bulb is nearer the surface. Each year new bulbs are formed at the end of runners from a parent bulb. These runners penetrate each year deeper into the soil. The deeper bulbs bear the flower stems. =933. Genus lilium.=—While the lily differs from either the trillium or erythronium, yet we recognize a relationship when we compare the perianth of six colored parts, the 6 stamens, and the 3-sided and long 3-loculed ovary. [Illustration: Fig. 496. Adder-tongue (erythronium). At left below pistil, and three stamens opposite three parts of the perianth. Bulb at the right.] =934. Family Liliaceæ.=—The relationship between genera, as between trillium, erythronium, and lilium, brings us to a still higher order of relationship, where the limits are broader than in the genus. Genera which are thus related make up the _family_. In the case of these genera the family has been named after the lily, and is the lily family, or _Liliaceæ_.