14 PROCEEDINGS OF THE AMERICAN ACADEMY. 



III. — A REVISION OF THE GENUS ZINNIA. 



ZINNIA, L. (Dedicated to Professor Johann Gottfried Zinn, of 

 Gottiiigen, born 1727, died 1759). — Heads radiate: disk-fiowers 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 cariuate, 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, 

 3-toothed, with or without 1 to 3 short or long awns. — Gen. ed. 6, no. 

 974; Gray, PI. 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. 22, fide Endl. Samritaliopsis, 

 Schz. Bip. ace. to Benth. & Hook, f., 1. c. — Annuals, perennial herbs, 

 or suffrutescent plants 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 8. United States to Chili and Brazil, but it 

 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 Sf Heterogyne, 

 Gray, 1. c. 



* Ligules showy, much exceeding the achenes, white or pale yellow. 



■1- Leaves 1-nerved. 



1. Z. acerosa. Gray. Leaves acerose, obscurely 1-nerved, much 

 crowded, rather sharp-pointed but scarcely pungent. 6 to 8 or 10 lines 

 long. — PI. AVright. i. 106. Diplothrix acerosa, DC. Prodr. v. 611. — -. 

 Hills of W. Texas, near Pecos, Wright, no. 324, Thurhcr, no. 125; 

 Mexico, San Luis Potosi, Berlandier, no. 1343, Parry ^ Palmer, no. 

 440^ ; Coahuila, Palmer, nos. 577, 578. 



