Acanthospermum. COMPOSURE. 230 



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

 DC. Prodr. v. .J17 ; Benth. cv Hook. Gen. ii. 349. 



* Perennial and the base sli^'litly ligneseent : akene with apex exposed at the hooded orifice of 

 the fructiferous bract: ray? plane, conspicuously exserted. comparatively ample, tardily decidu- 

 ous from the alvene, white! 



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

 ous or even ^ilvery-cane>';eijt mth a fine and mo-tly close pnl.escence, or greener and be- 

 coming strigulose : leaves linear or the lower lanee<-'lare or sjiatulate, entire or undulate, or 

 even sinuate-pinnatifid : peduncles slender; li^ules 5 to 9, cuneate-oblonL'. 2-3-lohed at apex, 

 3 to 6 lines lung: bracts of the involucre ovate, appresseJ, slicrlitly united at ba-e : frue- 

 tiferjui- bract- (2 lines Ions, including the hood) turbinate, nearly terete, sMuewhat incurved, 

 muricate with fharji tubercles; its hood about the length of the body and very ranch wider, 

 imperfectlv cupuliforra, nearly smourh, callous-thickened or becoming suberose. its truncate 

 and usually even margin commonly incurred. — Prodr. v. .51S (excl. habitat) ; Gray, PI. 

 Fendl. TS. PI. Wright., &c. if. leucanthum, Torr. & Gray, iX ii. 271. — Open ground, T\". 

 Arkansas and Texas to Arizona. (Adj. 5Iex.) 



— Var. ramosissimum. (J^- ramosissimuin,'DC. 1. c. by the char., but habitat and 



number of distribution of this and of 3/. cinereum were interchanged in the Prodroraus!) 

 ^lure locisely pubescent and diffusely branching : heads mostly smaller : hood of tlie fruc- 

 tiferous bract- with the less thickened margin little or not at all involute, sometimes ercse 

 or denticulate and bearing a mucro or sliut (seldom "tmcinate") cusp. — h juthern borders 

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



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

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

 corollas yellow. Our species all quite alike in fuliaL;e and habit. 



^M. hispidum, HBK. Hi^pidulous-hirsute, sometimes a foot high: rays very small, barely 



a line luug outer involucral bracts oval, distinct to the base; fructiferous bracts truncate 

 and not at all appendaged at the somewhat oblique summit, more or less taberculate on the 

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

 — S. Arizona, Wright, Dm mon. (Mex.) 



M. CUpulatuni, GR.iT. S' jmewhat hispidtilous-pubescent : rays small but exserted, 2 lines 

 Ions: outer involucral liracts connate to above the middle into an obtusely 5-lobed hemi- 

 spherical or sancer-sliaped cu].: fructiferous bracts nearly of tlie preceding. — Proc. Am. 

 -icad. viii. 291. — Borders of S Arizona, on the Mexican side, ■•^Jiott. (Mex.) 



M. longicornu, GE-iX. Sjiarsely hispidulons : rays exserted. obLing. when well devel- 

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

 fructiferous bracts more uervuse, little tuberculate or smooth, the summit cupulately pro- 

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

 fullv as long as the body, longer and more attenuate than in M. sfricevm, and sericeotis- 

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

 S5. — S. Arizona, Thurber. .SJ,ott. (Adj. Mex.) 



69. ACANTHOSPERMUM, Sdirank. ('AKai-^o, a prickle or thorn. 

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

 from the Viase ; with opposite dentate leaves, in their axils and in the forks small 

 suli=e-sile or short-peduncled heads of yellowish flowers : the (4 to 7) bur-like 

 involucral bracts eulardng in age. Xatives of the tropics, one or two species 

 becoming naturalized. — PL Ear. Hort. Monac. t. -53; DC. Prodr. v. .521. Ctn- 

 trospermum. HBK. Xov. Gen. & Spec. iv. 270. t. 3'J7. 



^^A. xaxthioi'des, DC. 1. c. Diffusely procumbent or creeping: stems pubescent: leaves 

 small (about inch long), mo^tly obovate. narrowed at base into a short petiole ; fructiferous 

 involucral bracts narrowly oblong, longitudinally >ukate. truncate, thickly beset especially 

 along the angles w-ith uniform and small hooked prickles. — A. Brasilum, Schrank. 1. c. ? 

 a hirsute forrn. Melampodivm australe, Loefl., L. Centrospermum xanthioides, HBK. L c. — 

 Eoadsides and waste grounds, S. Carolina to florida, &c. (Nat. from S. Amer.) 



