ARTICLE XX. 
Descriptions of new Species and Genera of Plants in the natural Order of the 
Composit, collected in a Tour across the Continent to the Pacific, a Residence 
in Oregon, and a Visit to the Sandwich Islands and Upper California, during 
the Years 1834 and 1835. By Thomas Nuttall. Read Oct. 2, 1840. 
Tribe I. VERNONIACE. | eam 
VERNONIA *spheroidea, pubescent; leaves lanceolate, serrate, beneath vil- 
lous; corymb compound, many-flowered, flowers small; involucrum subglo- 2 
bose, scales short and equal, tomentose and reflected —Has. Prairies of Ar- Age me 
kansas. 
Oxzs.—Remarkable for the reflection of the scales of the involucrum, which 
are all short, equal, and densely tomentose at the base and margins. 
Vernonia Arkansana, (DEcaND.) nearly smooth and herbaceous; leaves 
linear-lanceolate, very long, serrulate; corymb simple; flowers large, nearly all 
pedunculate, hemispherical; leaves of the involucrum lanceolate, terminating 
in very long, filiform, leafy, and spreading points.—Has. Plains of Arkansas, 
near Red River. | 
Oxss.—Remarkable for the great size of the heads of flowers, more than twice 
as large as in any other of our species, and also singular in the great length of 
the squamose points of the leaflets of the involucrum, which are a little pubes- 
cent. The leaves are very long, narrow, and smooth. Achenium somewhat 
pubescent. Pappus double, as usual. 
Missousi BOTANICAL 
Baspen Lisnary 
