. An illustrated flora of the northern United States, Canada and the British possessions, from Newfoundland to the parallel of the southern boundary of Virginia, and from the Atlantic Ocean westward to the 102d meridian. Botany; Botany. 342 AMBROSIACEAE. Vol. 4. Ambrosia psilostachya DC. Western Rag- weed. Fig. 4128. Ambrosia psilostachya DC. Prodr. 5: 526. 1836. Similar to the preceding species, but perennial by long rootstocks, the leaves thick, the pubescence stri- gose or hispid. Stems usually much branched, 2°-6° high, rather stout; leaves 1-2-pinnatind, 2-5' long, the lobes acutish
. An illustrated flora of the northern United States, Canada and the British possessions, from Newfoundland to the parallel of the southern boundary of Virginia, and from the Atlantic Ocean westward to the 102d meridian. Botany; Botany. 342 AMBROSIACEAE. Vol. 4. Ambrosia psilostachya DC. Western Rag- weed. Fig. 4128. Ambrosia psilostachya DC. Prodr. 5: 526. 1836. Similar to the preceding species, but perennial by long rootstocks, the leaves thick, the pubescence stri- gose or hispid. Stems usually much branched, 2°-6° high, rather stout; leaves 1-2-pinnatind, 2-5' long, the lobes acutish; racemes of sterile heads several or numerous, 2'-6' long, the, involucres campanulate, the receptacles chaffy; fertile heads mostly solitary, ovoid or obovoid, reticulated, short-pointed, unarmed,' or with about 4 short tubercles, pubescent, ii"-2" long. In moist open soil, Illinois to Saskatchewan, Texas, Mexico and California. July-Oct. 3. GAERTNERIA Med. Act. Pal. 3: 244. 1785. Phil. Bot. 45. 1789. [Franseria Cav. Icon. 2: 78. pi. zoo. 1793.] Hispid or tomentose branching herbs, with the aspect of Ambrosias, sometimes woody at the base, with mostly alternate lobed or divided leaves, and small monoecious greenish heads of discoidal flowers, the staminate in terminal spikes or racemes, the pistillate solitary or clustered in the upper axils. Involucre of the pistillate heads ovoid or globose, closed, 1-4-celled, 1-4-beaked, armed with several rows of spines and forming a bur in fruit; corolla none or rudimentary; style deeply bifid, its branches exserted; stamens none; achenes obo- void, thick, solitary in the cells; pappus none. Staminate heads sessile, or short-peduncled, their involucres broadly hemispheric, open, 5-12-lobed; receptacle chaffy; corolla regular, the tube short, the limb 5-lobed; style undivided; anthers scarcely coherent; mucronate-tipped. [In honor of Joseph Gaertner, 1732-1791, German botanist] About 25 species, natives of America. In additio
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