' S[LFHIUM, a genus of plants belonging to the order composite'. Generic characteris tics: heads many-flowered, radiate; rays numerous, pistillate and fertile; ovaries in two or three rows; disk flowers apparently perfect, but with undivided style and sterile; scales of the broad and flattish involuere imbricated in several rows, broad, and with loose, leaf-like summits, except the innermost, which are small. They are tall, coarse, perennial herbs, having a copious resinous juice, and large corynbose-panieled yellow lowering heads. Silpitium, lancinAtturn, called and compass-plant, is rough and bristly, growing from 3 to ft ft. high; leaves pinnately parted, with divisions lan ceolate or linear, rarely entire: scales of the involucre ovate, tapering into long -and spreading rigid points; achenia, or one-seeded capsule, broadly winged and deeply notched. IL grows on the prairies of Michigan, Wisconsin, and southward and west ward: blossoms in July. It is called compass-weed from its reputed property of grow ing so as to point its leaves to the cardinal points of the compass. Another species, S.
terebeathineweata, the prairie burdock, grows from 4 to 10 ft. high, with many small heads iii a panicle at the top; leaves ovate-cordate, serrate toothed, thick, rough, more so beneath, and from 1 to 2 ft. long on slender leaf-stalks. A variety,pinnaiijiaum, has deeply cut. or piunatitid leaves. It grows on prairies and oak openings, Ohio, Mi:Lhi gan, Wisconsin, and southward: blooms in July and September. Other species are S. trifolecawn, S. asterixcus, S. integrifohom, and 8. perfolitttum, the cup-plant, which grows from 4 to 8 ft. high, having ovate leaves, coarsely toothed, the upper united by their .bases, forming a cup-shaped disk; heads corymbose, and acheniaiwinged and variously notched: grows on rich soils along streams in Michigan, Wisconsin, and southward. Also escaped from gardens blossoms in July.