Acanthospermum. .COMPOSITE. 239 



others conspicuous. — Gaertn. Fruct. t. 1G9; R. Br. in Linn. Trans, xii. 104; 

 DC. Prodr. v. 517; Benth. & Hook. Gen. ii. 349. 



* Perennial and tlie base sliglitly lignescent : akene with apex exposed at the hooded orifice of 

 the fructiferous bract : raj-s plane, conspicuously exserted, comparatively ample, tardily decidu- 

 ous from the akene, white ! 



M. cinereum, DC. Bmuclied from the base, a span to a foot high, rather slender, cinere- 

 ous or even silvery-canescent with a fine and mostly close pubescence, or greener and he- 

 coming strigulose : leaves linear or the lower lanceolate or spatulate, entire or undulate, or 

 even sinuate-pinnatifid : peduncles sleuder : ligules 5 to 9, cuneate-oblong, 2-3-lobed at apex, 

 3 to 6 lines long : bracts of the involucre ovate, appressed, slightly united at base : fruc- 

 tiferous bracts (2 lines long, including the hood) turbinate, nearly terete, somewhat incurved, 

 muricate with sharp tubercles ; its hood about the length of the body and very much wider, 

 imperfectly cupuliform, nearly smooth, callous-thickened or becoming suberose, its truncate 

 and usually even margin commonly incurved. — Prodr. v. 518 (excl. habitat) ; Gray, I'l. 

 Pendl. 78, PI. Wright., &c. M. Icucanthiun, Torr. & Gray, Fl. ii. 271. — Open ground, W. 

 Arkansas and Texas to Arizona. (Adj. Mex.) 



Var. ramosissimum. (M- ramosissimum, DC. 1. c. by the char., but habitat and 

 number of (listriliution of this and of M. cinereum weve. interchanged in the Prodromus!) 

 More loosely pubescent and diffusely bi-anching: heads mostly smaller : hood of the fruc- 

 tiferous bracts with tlie less thic.kened margin little or not at all involute, sometimes erose 

 or denticulate and bearing a mucro or short (seldom "uncinate") cusj). — Southern borders 

 of Texas, Berlandier, Palmer. (Adj. Mex.) 



* * Animals, commonly low, erect, branching, with linear or oblong mostly entire leaves: akene 

 with merely the apex exposed at the summit of tlie enclosing fructiferous bract: ray and disk- 

 corollas yellow. Our species all quite alike in foliage and habit. 



M. hispidum, HBK. Ilispidulous-liirsute, sometimes a foot high: rays very small, barely 

 a line long • outer involucral bracts oval, distinct to the base ; fructiferous bi-acts truncate 

 and not at all appeudaged at the somewhat oblique summit, more or less tubercnlate on the 

 back and sides. — Nov. Gen. & Spec. iv. 273, t. 399; DC. 1. c. 520; Gray, IT. Wright, ii. 85. 

 — S. Arizona, Wri(jlit, Lemmon. (Mex.) 



M. CUpulatum, Gray. Somewhat hispidulous-pubescent : rays small hut exserted, 2 line.s 

 long : outer involucral bracts connate to above the middle into an obtusely 5-lobed hemi- 

 spherical or saucer-siiaped cup: fructiferous bracts nearly of the preceding. — Proc. Am. 

 Acad, viii. 291. — Borders of S. Arizona, on the Mexican side, Scliott. (Mex.) 



M. longicornu, Guay. Sparsely hispidulous : rays exserted, oblong, when well devel- 

 oped 3 lines in length and as long as the involucre, the outer bracts of which are distinct: 

 fructiferous bracts more uervose, little tubercnlate or smooth, the summit cupulately pro- 

 duced and gradually extended exteriorly into a circinnate or revolute horn or rigid awn, 

 fully as long as the body, longer and more attenuate than in M. serlceum, and sericeous- 

 pubescent along the outside. — Mem. Amer. Acad. (PI. Tliurb.) v. 321, & Bot. Mex. Bound. 

 85. — S. Arizona, Thurber, Schott. (Adj. Mex.) 



69. ACANTHOSPERMUM, Schrank. {"kKavOa, a prickle or thorn, 

 and a-Trkpjxa, seed, i. e. prickly-fruited.) — Homely annual weeds, much branched 

 from the base ; with opposite dentate leave.?, in their a.xils and in the forks small 

 subsessile or short-peduncled heads of yellowish flowers ; the (4 to 7) bur-like 

 involucral bracts enlarging in age. Natives of the tropics, one or two species 

 becoming naturalized. — PI. Rar. Hort. Monac. t. 5.'5 ; DC. Prodr. v. 521. Cen- 

 trospermum, HBK. Nov. Gen. & Spec. iv. 270, t. 397. 



A. XANTiiiofDES, DC. 1. c. Diffusely procumbent or creeping : stems pubescent : loaves 

 small (about inch long), mostly ol)ovate, narrowed at base into a short petiole : fructiferous 

 involucral bracts narrowly oblong, longitudinally sulcate, truncate, thickly beset especially 

 along the angles with uniform and small hooked prickles. — A. Brasiinm, Sclirank, I.e.? 

 a hir.'^ute form. Melainjiodium ausfrale, Loefl., L. Centrospermum xantliioides, HBK. 1. C. — 

 Koadsides and waste grounds, S. Carolina to Florida, &c. (Nat. from S. Amer.) 



