AND GENERA. OF PLANTS. 347 



Achenium oboval, compressed, but somewhat turgid. — Tall annuals with 

 opposite, ovate, serrated leaves, hirsutely canescent beneath ; the flowers in 

 terminal, naked, spiked panicles; in the fertile plant the spikes are filiform 

 and interrupted. — Almost intermediate with Ambrosia and Iva. — (The name 

 from nixporyjs, bitterness; in allusion to the qualities of the plant.) 



Iva * paniculata. 



Hab. In the Rocky Mountains, by streams, in alluvial wastes. A rather tall annual, with long, 

 petiolated leaves ; the stem simple, terminating in a naked, branching, pyramidal panicle of green- 

 ish, inconspicuous flowers. Involucrum about five-leaved, obtuse ; male capitulum about fifteen- 

 flowered, with minute rudiments of female flowers ; in the fertile capitulum the female flowers are 

 about eight. 



Iva xanthifolia; Q, leaves lanceolate-ovate, serrate, acuminate, long petio- 

 late, appressed pilose, and canescent beneath; capituli somewhat spiked; se- 

 pals ovate, acuminate. — Nutt. Gen. Am., Vol. II., p. 185. Decand., Vol. 

 v., p. 529. Nearly allied to the preceding. 



Division. PARTHENIEiE. 



*BOLOPHYTA. 



Capituli many-flowered, heterogamous; rays feminine in one series, about five, 

 ligulate, nearly tubular, very short, truncated and crenulate ; radial florets 

 tubular, five-toothed, masculine, with a simple stigma. InvolXicrum hemi- 

 spherical, biserial, external scales ovate, internal suborbicular. Receptacle 

 conic, paleaceous, the palea sheathing, wider and pubescent at the summits. 

 Stigmas of the ray short, smooth and obtuse. Achenium compressed, some- 

 what obcordate, with a cartilaginous margin, to which it is ingrafted on 

 either side with the two anterior palese^ and with which, and the contiguous 

 scale of the involucrum, it is at length deciduous. Pappus none, the ache- 

 nium crowned with the small, persisting ligula. — An alpine, csespitose, stem- 

 less, small perennial, with a long, almost ligneous root, crowned with dense 

 and numerous vestiges of former leaves, based by tufts of hairs; leaves spathu- 

 late-linear, narrow and entire, canescent with appressed, strigose hairs; flow- 

 ers solitary, sessile, or short pedunculate, scarcely arising beyond the sum- 



