344 COMPOSIT.E. Hijmenodea. 



with 9 to 12 broad and silvery-scarioua persistent wings: corolla none. Akene as 

 in Ambrosia, S:.c. — Low and much branched hhnibby plants, of arid deserta, Arto- 

 jnitiia-liku in habit; with idturnatu linuui^lilifonn luavua, minutely canesoont beneath, 

 the lower sparingly pinnately i»arted, and small lieada sessile in i)rofu8o panielt)(l 

 clusters. — ri. lu-ndl. 7'J ; Torr. VI l''remont. t. 8. 



1. H. Salsola, Torr. & Gray. Fruiting invulucre spindle-shaped and strobile- 

 like, being covered with the spirally disposed orbicular scales (each a quarter of an 

 inch long), which are imbricated when moist, but spreading when mature and dry. 



Sandy saliiio upliinda near tlie Mohave lliver (Fremont, Cooper), and through tlie desert interior 

 to N. W. Nevada, on the borders of CaUt'ornia, JFalii07i, Leiiimon. 



2. H. monogyra, Torr. & Gray. Fruiting invohicre smaller (2 lines long), 

 bearing at the muldle a single whorl of obovate or rhombic-reniform radiating scales. 



Kiver liottonis, San Diego {Cleveland), thence to tlie Gila : not rare in Arizona, &c. Plant 

 3 to 5 feet liigh. Tlie young plant so named in the Botany of King's Expedition belongs to the 

 preceding species. 



40. AMBROSIA, Tourn. UA(iWKKn. 

 Heads homogamous and unisexual, niona'cious (sometimes nearly dioecious) ; the 

 pistillate one-llowered, mostly in the axils of npi^sr leaves ; the staminate several- 

 llowered in panicled or single terminal racemes or spikes, without bracts. Stand- 

 nate flowers in an open seveml-lobed or almost entire truncate herbaceous involucre, 

 subtended by slender or filiform chaff; their corollas broad and 5 • toothed ; their 

 anthers almost distinct, tipped with a slender-acuminate inflexed appendage ; ovary 

 and stigma none or rudimentary ; style with truncate tip radiately timbriate. Pis- 

 tillate tlower in a closed akeno-like one-celled involucre, which at maturity is armed 

 below the short rigid beak with a single row of 4 to 8 tubercles or short spines, or 

 sometimes naked : corolla none. Akene ovoid or obovate, thick : pappus none. — 

 Weedy coarse annuals, or perennials, with mostly lobed, pinnatifid, or piniialely 

 divided and cleft leaves, the lower at least opposite ; the small heads greenish, or 

 the sterile flowers barely yellowish. Chiefly American and widely diff"used, but 

 apparently very scanty in California. 



1. A. artemisiaefolia, Linn. Annual, 1 to 3 feet high, roughish-hirsute : 

 leaves thinnish, twice pinnatihd : fruit (i. e. fruiting involucre) smooth below, not 

 reticulated, armed with about ti very acute horns or spines. 



This, the common JioiiuDt IVormicood or Bitter weed of the East, can hardly be absent from 

 California. S. IValson collected it in Nevada, and others in Oregon. 



2. A. psilostachya, UC. Perennial, more strigosely hirsute than the forego- 

 ing, with thicker and less divided leaves, the upper only once pinnatifid : fruit 

 puberulent, rugose-reticulated, without horns or spines, or with short and rather 

 blunt ones. — A. coronopifoiia, Torr. & Gray, Fl. ii. 291. 



San Luis \\i.'.y {Coulter, Parry); l?ay of San Francisco {Pickering &w\ Brackenridfje) ; San 

 Diego Co., I'aliiicr. Also in Nevada, and thenco eastward lo Texas and Illinois. 



41. PRANSERIA, Cav. 

 Heads, flowers, &.c., as in Ambrosia, except that the fertile involucre is armed 

 with more than one rank of prickles or spines, and is l-4:-celIed and 1 -4-flowered. 

 — All American herbs or suffrutescent plants; the greater part North American 

 west of the Mississippi. 



