Hymenodea. COMPOSITE.. . 343 



37. OXYTENIA, Nutt. 

 Head heterogamous, discoid, about 5 marginal flowers pistillate and apetalous, 

 consisting merely of ovary and 2-cleft style; the other flowers 10 to 20, staminate 

 (their ovary and stigma abortive), Avith funuelform 5-Iobed corolla and uiulivided 

 style, and nearly distinct anthers, these with blunt tips. Involucre of about 5 thin 

 and broad scales. Eeceptacle chaffy, a spatulate villous scale subtending each or 

 most of the sterile flowers and falling with them. Akencs obovate, turgid, beset 

 "with long villous hairs, crowned (at least when young) with a largo and protu- 

 berant annular disk. Pappus none. — Genus nearly related to the next, of one 

 species, viz. 



1. O. acerosa, Nutt. Shrubby, 3 or 5 feet high, whitened with a fine pubes- 

 cence : branches rigid, rush-like, mostly naked, terminated by the racemose or 

 paniculate-clustered inflorescence of small woolly heads : leaves as far as known 

 alternate, either pinnately 3 - 5-foliolate or the uppermost simple and like tlie leaf- 

 lets, i. e. very narrowly linear and revoluto so as to appear filiform or acerose, 2 to 4 

 inches long, rigid. — PI. Gamb. 172. 



Southeastern borders of California and adjacent parts of Arizona, in a desert region, Gambel, 

 Lieut. Wheeler. 



38. IVA, Linn. 



Head heterogamous, discoid ; a few marginal flowers pistillate and with a short 



tubular corolla ; the other and more numerous flowers staminate (their ovary and 



stigma abortive), with funnolform 5dobcd corolla and undivided style: anthers 



nearly distinct. Scales of the involucre few and mostly in a single series, commonly 



united into a cup. Receptacle chaffy with linear or spatulate scales subtending 



sterile flowers. Akenes obovate, thick, naked, often granulate ; no disk at the apex. 



— Leaves simple, at le.ast some of the lower opposite. Heads small, nodding on 



short pedicels, either in the axils of the leaves, or in terminal spikes or panicles. 



A genus of several species on the eastern side of the continent, one of which extends from the 

 Missouri llivor to tlio Pacific, viz. 



1. I. axillaris, Pursh. Perennial, branching, a span to a foot and a half high, 

 varying from minutely hirsute to glabrous, and the sessile entire leaves from 

 broadly linear to spatulate or obovate (about an inch long) : heads solitary in their 

 axils, hemispherical : scales of involucre about 5, broad, united at base or beyond 

 the middle. 



Var. pubescens. Villous with lax spreading hfiirs ; the involucre turbinate and 

 almost entire. — Gray in Bot. "Wilkes Exp. 350. 



Sandy and usually saline soil, near the coast, also along the western borders of the State, and 

 north to British Columbia. The variety from bay of Sun Francisco. 



39. HYMENOCLEA, Torr. k Gray. 

 Heads homogamous and unisexual, monoecious ; the staminate ones many-flow- 

 ered ; the pistillate one-flowered ; the two kinds intermixed in the axillary sessile 

 clusters, or the staminate in upper axils. Staminate flowers in a hemispherical 

 licad, with an open 5-C-lobpd iiivolucro, similar to those of ylvihmsia (oidy the 

 chair of the receptacle is much dilated, and the inflexed tip of the anthers is blunt): 

 pistillate flower solitary in a closed and akenedike involurro, which is pointed with 

 a slender beak from the tip of which the style protrudes, its middle adorned 



