14 PROCEEDINGS OF THE AMERICAN ACADEMY. 
Iil.—A REVISION OF THE GENUS ZINNIA. 
ZINNIA, L. (Dedicated to Professor Johann Gottfried Zinn, ot 
G6ttingen, born 1727, died 1759). — Heads radiate: disk-flowers her- 
maphrodite, fertile; ray-flowers pistillate, fertile, with suborbicular oval 
or oblong sessile persistent white, yellow, red, or purple ligules. Involucre 
ovate-cylindric or campanulate, the scales 3 —many-seriate, broad, closely 
imbricated, obtuse or rounded, often more or less colored and slightly 
inflated or subsquarrose just beneath the summit. Disk conical to colum- 
nar: chaff scarious, more or less carinate, enveloping the flowers, often 
erose at the mostly obtusish apex. Corollas of the disk-flowers tubular 
with narrow scarcely ampliate throat and 5-toothed limb. Anthers ap- 
pendaged at the apex, entire at the base. Style-branches obtuse, scarcely 
or not at all appendaged. Achenes laterally compressed, glabrous or cilio- 
late on the edges, 2-toothed at the summit and frequently 1-awned from 
the inner angle or rarely 2-awned ; the achenes of the rays triquetrous, 
8-toothed, with or without 1 to 3 short or long awns. — Gen. ed. 6, nd. 
974; Gray, Pl. Wright. i. 105; Benth. & Hook. f. Gen. ii. 357; 
Hoffm. in Engl. & Prantl, Nat. Pflanzenf. iv. Ab. 5, 225. Orassina, 
Scepin. Diss. and Lejica, Hill, Exot. Bot. t. 29, fide Endl. Sanvitaliopsis, 
Schz. Bip. acc. to Benth. & Hook. f., 1. e. — Annuals, perennial herbs, 
or suffrutescent piants with opposite mostly entire leaves and showy 
terminal pedunculate or subsessile heads. About a dozen species known 
in nature, and three or four others somewhat doubtfully distinguished in 
horticulture, beside obviously artificial varieties and hybrids. The range 
of the genus is from the S. United States to Chili and Brazil, but 1 
attains its greatest specific diversity in Mexico. 
§ 1. Low cespitose perennials, shrubby at the base and many- 
stemmed : stems (or perhaps better subsimple branches) erect, crowded, 
or fastigiate : root stout, ligneous : leaves strictly linear to acerose, often 
fascicled and rigidulous, mostly rather pale. —§§ Diplothrix § Heterogyn 
Gray, 1. c. 
* Ligules showy, much exceeding the achenes, white or pale yellow. 
+ Leaves 1-nerved. 
Vs 1. Z. acerosa, Gray. Leaves acerose, obscurely 1-nerved, much 
/ crowded, rather sharp-pointed but scarcely pungent, 6 to 8 or 10 lines 
long. — Pl. Wright. i. 106. Diplothrix acerosa, DC. Prodr. v- ai 
Hills of W. Texas, near Pecos, Wright, no. 324, Thurber, no. 1253 
Mexico, San Luis Potosi, Berlandier, no. 1343, Parry § Palmer, 2° 
4403; Coahuila, Palmer, nos. 577, 578. ei a 
