Par? 1, 1922] AMBROSIACEAE 19 
ulent and reticulate above the spines; beak stout, fully 1 mm. long; spines 5-7, rather small, 
less than 0.5 mm. long. 
TYPE LOCALITY: “‘ Virginia.’ 
DISTRIBUTION: Maine to aes and District of Columbia. 
ILLUSTRATIONS: Lam. Tab. Encyc. pl. 765, f. 1; Rep. Comm. Agr. U. S. 1886: Bot. pl. 9. 
10. Ambrosia media Rydb. Bull. Torrey Club 37: 127. 1910. 
An annual herb, with branched roots; stem 4-6 dm. high, hispid with ascending or ap- 
pressed hairs, more or less strigose; leaves pinnately divided or the upper merely cleft, 5-10 
cm. long, scabrous and glandular-granuliferous above, hispid-strigose beneath; petioles 1-2 
cm. long, hirsute-ciliate; blades ovate in outline; divisions oblong or lanceolate, the lower 
usually lobed or toothed, acute; staminate heads usually numerous, in racemes terminating 
the branches, cr in the predominantly pistillate form few; involucre 5-lobed and crenulate, 
4-5 mm. broad, hispid-strigose; paleae of the receptacle filiform or stubulate; corolla puberu- 
lent; pistillate heads in few (or in the predominantly pistillate form numerous) small clusters 
in the upper axils; body of the fruit obovoid, 3 mm. long, puberulent-strigose or in age gla- 
brate; beak fully 1 mm. long, pubescent; spines 5-7, sharp, subulate, 0.5 mm. long. 
TYPE LOCALITY: Fort Collins, Colorado. 
DISTRIBUTION: Saskatchewan to Kansas, New Mexico, Nevada, and Washington. 
11. Ambrosia Rugelii Rydberg, sp. nov. 
An annual herb, with branched roots; stems 3-6 dm. high, densely hirsute, with spreading 
hairs; leaves 5-8 cm. long, peticled, pinnately divided, dark-green, when dried almost black, 
hispidulous on both sides, thick and strongly veined; petioles very short or those of the upper 
leaves none; blades ovate in outline; segments oblong, acute, toothed; staminate heads usually 
numerous, in racemes terminating the branches; involucre 5-lobed and crenate, 3-3.5 mm. 
broad, hispidulous; paleae of the receptacle filiform; corolla puberulent; pistillate heads few, 
in small clusters in the axils of the upper leaves; body of the fruit 2.5-3 mm. long, puberulent; 
beak less than 1 mm. long; spines 5-6, sharp, conic-subulate, 0.3-4.0 mm. long. 
Type collected in Florida, 1845, Rugel 508 (herb. N. Y. Bot. Gard.; cotype, U. S. Nat. Herb.). 
DISTRIBUTION: Florida and Georgia. 
12. Ambrosia longistylis Nutt. Trans. Am. Phil. Soc. II. 7: 344. 
1840. 
Ambrosia artemistifolia octocornis Kuntze, Rev. Gen. 305. 1891. 
An annual herb, with branched roots; stem 2-3 dm. high, scabrous-hispidulous, the hairs 
with pustulate bases; leaves pinnately divided, 3-7 cm. long, scabrous-hispidulous as the stem, 
dark-green, strongly ribbed; petioles 1-2 cm. long, often wing-margined, hispidulous; blades 
ovate in outline; lobes oblong, mostly entire; staminate heads in a terminal raceme; involucre 
4-5 mm. broad, 5-lobed, with broadly triangular acutish lobes, hispidulous, the hairs with 
strongly pustulate bases; paleae of the receptacle filiform; pistillate heads usually many in 
small clusters in the upper axils; style described as being an inch long, but in the type only 
about 5 mm. long; body of the fruit obovoid, 3 mm. long, hispidulous, variegated; beak about 
2 mm. long; spines 6-8, subulate, 0.6-0.7 mm. long, erect. 
TYPE LOCALITY: “Rocky Mountains.’’ 
DISTRIBUTION: Western Nebraska and Wyoming. 
13. Ambrosia psilostachya DC. Prodr. 5: 526. 1836. 
Ambrosia Lindheimeriana Scheele, Linnaea 22: 156. 1849. 
Ambrosia coronopifolia var. [asperula, &c.] A. Gray, Bost. Jour. Nat. Hist. 6: 226. 1850. 
Ambrosia psilostachya Lindheimeriana Blankinship, Rep. Mo. Bot. Gard. 18: 173. 1907. 
Ambrosia psilostachya asperula (A. Gray) Blankinship, MS. 
A perennial herb, with a creeping rootstock; stem 3-6 dm. high, branched above, striate, 
hirsutulous with short ascending hairs; leaves subsessile, lanceolate in outline, pinnatifid, 
scabrous-hirsutulous and glandular-granuliferous, the hairs with pustulate bases; divisions 
linear-lanceolate, acute or acuminate, entire or the lower few-toothed; staminate heads numer- 
