Hofmeisteria. COMPOSITE. 93 



MargacoJa pnrvula, Buckl. in Proc. Acad. Pliilad. 1861, 1862. — 'SVet ground in prairies, 

 Texas, Wright, Buckle >/, &c. (Mex., Palmer.) 

 T. rivularis, Gray, 1. c. Stems floating, in shallow water rooting, and flowering branches 

 emersed and ascending: leaves succulent, mostly opposite, an inch or two in length, cuneate- 

 obovate, sparingly incised or palmately 3-lohed, contracted into a narrow connate-clasping 

 auriculate base : heads fewer or solitary on simple peduncles, 3 or 4 lines in diameter : 

 involucral bracts about 12, oval, obtuse : receptacle highly convex: tube of corolla slender, 

 equalling the hemisplierical throat and limb : style-branches flat and linear, acutish : pappus 

 a minute and evanescent or obscure setulose crown. — In springs and streamlets, S. W. 

 Texas, Wright, &c. (Adjacent Mex., Gregg, &c.) 



7. AG-ERATUM, L. (Ancient Greek and Latin name of some aromatic 

 plant of this order, probably an Achillea, from a privative and yr/pas, yTyparos, 

 not waxing old, transferred by Linnaeus to an American genus.) — Chiefly 

 tropical, herbaceous, and with opposite petiolate leaves ; heads small in terminal 

 corymbiform cymes or rarely paniculate ; flowers blue, jiurple, or white, in 

 summer. — Benth, & Hook. Gen. ii. 241, excl. syn. Oxi/lobus. Ageratum & 

 Ccelestina, Cass., DC. ; to which should be added Alomia, HBK., differing only 

 in the want of papjDus. 



§ 1. Eu AGERATUM. Paiijius of distinct aristate or sometimes muticous paleae : 

 receptacle naked. 



A. coxTzofDES, L. Annual, pubescent : leaves ovate or deltoid-subcordate, crenately serrate : 

 pappus of 5 to 7 lanceolate rigid scales, mostly tapering into a scabrous awn which nearly 

 equals the blue or white corolla. — Schk. Handb. t. 238 ; liook. Exot. Fl. t. 15. A. Mexicunum, 

 Sims, Bot. Mag.t. 2524, &c., a more pubescent form, common in oruaTuental cultivation. — 

 Sparingly naturalized near towns in the S. Atlantic States. (Nat. from Trop. Amer., &c.) 



§ 2. Ccelestina. Pappus coroniform or cujiulate (by the union of the palese 

 into an entire or toothed cup or border), sometimes obsolete. — Ccelestina, Cass,, 

 DC, &c. (In our species the receptacle is naked, duration of root uncertain, 

 and flowers usually blue or violet.) 



A . corymbosum, Zuccagni. Scabrous-pubemlent, erect : leaves short-petioled, ovate 

 to oblong-lanceolate, irregularly few-several-toothed : floriferous branches naked above : 

 corolla-tube glanduliferous : pappus prominently cupulate, more or less dentate. — Zuccagni 

 ex Balb. in Hort. Taur. 1806; Pers. Syn. ii. 402. A. cosiest inum, Sims, Bot. Mag. t. 1730; 

 Lodd. Bot. Cab. t. 623. Ccelestina ageratoides, HBK. Nov. Gen. & Spec. iv. 151 ; Gray, PI. 

 Wright, ii. 70. C. ccerulea, Cass. Diet. vi. suppl. 8, t. 93. C. corj/mbosa, DC. Prodr. v. 108. 

 — New Mexico, Wright, &q. (Mex.) 



A. littorale, Gray. Glabrous, decumbent or assurgent : leaves rather succulent, long-peti- 

 oled, ovate with cuneate base, serrate : corolla glabrous : pappus an extremely short ci-own, 

 with or without several minute narrow teeth, or reduced to a mere ring. — Proc. Am. Acad. 

 xvi. 78. — Ccelestina maritima, Torr. & Gray, PI. ii. 64; not Ageratum niaritlmum, HJiK., 

 which is a true Ageratum with diminutive pappus. — Key West, S. Florida, Bennett, Blod- 

 gett, Palmer, Garber. 



8. HOFMEISTERIA, Walp. (W. Hofmeister, a vegetable histologist.) 

 — Low suffrutescent 2>lants ; with heads terminating slender peduncles, small 

 incised leaves either opposite or alternate on long jjetioles, and whitish flowers ; 

 the style-branches clavate. — Two sjiecies, " the original one (H. fascicidata, 

 "Walp. Rep. vi. 106 ; Helogyne, Benth. Bot. Sulph. 20, t. 14), of Lower California, 

 with 2-3-awned pappus. 



H. pluriseta, Gray. Slightly pulierulent and viscidulous, much branched : leaves with small 

 (2 to 5 lines long) deltoid to oblong blade very much shorter than the petiole : heads about 



