490 COMPOSITE. Troximon. 



on the broad midrib ; the often undulate margins tomentose ; scales of the in- 

 volucre somewhat scarious, lanceolate, cuspidate-acute, glabrous, in two 

 nearly equal series, erect ; bristles of the pappus very numerous, rigid; the 

 inner and stronger series evidently flattened and dilated towards the base ! — 

 Pursh,fi. 2. p. 742. T. marginatum, Null.! gen. 2. p. 128, <!^' in trans. 

 Amer. phil. soc. {n. ser.) 7. j)- 433. 



Plains of the Upper Missouri and Platte to the Rocky Mountains, Brad- 

 hury ! Nuttall ! Mr. Nicollet! Eagle Prairie, Wisconsin, Mr. Lapham ! 

 April-June. — Heads, &c., apparently rather smaller than in the following. 

 Acheuia manifestly obcompressed, obtusely ribbed, a little narrowed at the 

 summit, but not at all rostrate, much shorter than the setose pappus. 



2. T. giaucum (Nutt.) : somewhat glaucous; leaves linear-lanceolate, 

 acute, entire, Or rarely with one or two small teeth (the broad midrib some- 

 what nervulate towards the base), and with the scape nearly glabrous ; scales 

 of the involucre loosely imbricated in 3-4 series, somewhat unequal ; the 

 exterior (green) ovate-lanceolate and more or less pubescent when young ;" 

 bristles of the pappus capillary, rigid. — Nntt. ! in Fras. cat. (1813), <^' gen. 

 2. p. 128 ,• PursKJi. 2. p. 496 <V 506 ; Sims, bot. mag. t. 1667 ; Hook. ! fl. 

 Bor.-Am. 1. p. 300. (var. (i.) 



(3. dasycephaluni : involucre woolly at least when young, the exierior 

 scales spreading ; leaves and scape often somewhat pubescent ; receptacle 

 sometimes, but not always, furnished with a few linear-acuminate chaffy 

 scales intermixed among the flowers! — T. giaucum, Richards..' appx. 

 Frankl. journ. ed. 2. p. 29 ; DC. prodr. 7. p. 252. T. giaucum, a. Hook. ! 

 fl. Bor.-Am. 1. p. 300; 6f bot. mag. t. 3462. T. pumilum, Nutt. in trans. 

 Amer. phil. soc. I. c. ? Ammogeton scorzoneraefolium, Schrad. ! ind. sem. 

 Gait. 1833 ; DC! prodr. 7- p. 98. 



Grassy plains of the Upper Missouri, Bradbury, Nuttall! Dr. James ! and 

 Big Sioux River, Mr. Nicollet! to Saskaichawan, Drummond ! (3. Saskat- 

 chavvan and prairies of the Rocky Mountains to the Arctic coast, Drummond ! 

 Richardson! July-Aug. — Scape 6-12 inches high. Leaves 6-8 inches 

 long, 4-10 lines wide. Heads nearly an inch in diameter. Tube of the 

 bright yellow corolla beset with long jointed hairs near the summit. Achenia 

 abruptly narrowed at the apex, obcompressed, at least when young. — It is 

 remarkable that the chaff' on the receptacle of the var. ,3. is found in some 

 but not all of the wild specimens we have examined. 



3. T. parviflorum (NuXl.) : glabrous, or somewhat villous-pubescent when 

 young; leaves narrowly lanceolate-linear, acute or acuminate, entire, some- 

 times retrorsely denticulate towards the base ; scales of the glabrous invo- 

 lucre ovate-lanceolate, acuminate, few, in 2-3 series ; the outer bracteolate, 

 scarcely half the length of the inner; pappus capillary, rigid. — Nutt.! in 

 trans. Amer. phil. soc. I. c. 



Plains of the Platte to the Rocky Mountains, Nuttall ! Lieut. Fremont ! — 

 Scape 4-5 inches high, mostly longer than the leaves: the latter about 2 lines 

 wide. Head very much smaller and narrower than in the preceding ; the 

 flowers and involucral scales much fewer. Flowers yellow, sometimes 

 changing to rose-color in drying. 



4. T. roseum (Nutt.) : leaves runcinate-pinnatifid, with short linear lobes, 

 and with the scape sparsely villous-pubescent when young; scales of the 

 glabrous involucre lanceolate, acuminate, few, in 2-3 series, the exterior 

 short; pappus copious, capillary, rigid (flowers rose-color). — Nutt.! in trans. 

 Amer. phil. soc. I. c. 



Plains of the Platte, with the preceding, " which it wholly resembles, ex- 

 cept the leaves and red [rose-color in spec, char.] flowers," Nuttall! — Ache- 

 nia with 10 sharp ribs, rathsr shorter than the pappus, narrowed at the apex 



