BOTANY. 



87 



\ inclusus, slmplicissimus. Ovarium nullnm. Aclienia obcompresso-plana, ala laclniata clrcum- 



data^ cimi squamis fructiferis petaloideo-scariosis iis majoribus involucruin externum multotics 

 superantia. Pappus "brevis, plurisetulosus, deciduus vel cvanescens. — Ilcrba liuinilis, rauiutia, 

 hispidulo-canescensj alternifolia; capitulis racemoso-paniculatis, fructiferis cernuis. 



D. CANESCENS. In the sandy desert of the Gila and of the Colorado ; Emory. A small speci- 

 men of this curious plant was brought home by Col. Emory from his reconnaissance of the Gila, 

 etc. J in 1846; but it has not again been met with. The base of the plant is unknown. Leaves, 

 at least the upper oneS; alternate^ oval^ obtusely dentate^ on slender petioles^ scabrous or hispid, 

 and when young canescently villous on both sides; those of the flowering branches gradually 

 reduced to small and spatulate bracts. Heads short-pedicclled, arranged in loose and nearly 

 leafless spikes or racemes^ which are panicled at the summit of the stem in anthesls^ only one 

 and a half lines long ; but in fruit the whitish and somewhat glandular and erose j air of inner 

 involucral scales become three or four lines long and almost as broad ; they are loosely appressed 



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to the achenia which they subtend, and appear to be deciduous with them at maturity. The 

 mature achenia are about 3 lines long, and 2 lines wide, including the strong laciniate-toothed 

 and incised wing, both faces slightly hispid^ and carinately one-nerved in the middle ; near the 

 summit of the nerve of the inner, and sometimes of the outer face also, a small crest often appears 

 like the rudiments of an anterior and posterior wing. Although the full-grown achenia com- 

 monly appear destitute of a pappu?, yet in the flowering state there is always a rather con- 

 spicuous ring of short bristles surrounding the base of the naked style, and traces of it are 

 generally discernible at maturity. The bristles are united at the base into a ring, and appear 

 to form a true pappus. They consist, however, of single rows of cells, exactly like the short 

 and fine bristly hairs which fringe the margin of the inner involucral scales. It will be seen 

 that the genus belongs to the division Ivea3 of De Candolle. The name (from or<T, two, and 

 Kopicr^ a bug,) alludes to the two achenia appearing like bugs, or like the achenia of some species 



of Coreopsis. 



Ambroisa psilostachya, do. Prodr. 5, p. 526 ; Gray^ PI. Wright^ I. c. A. coronopifolia, Torr. 



& Gray. Common, from Texas to Sonora. It occurs both with unarmed and tuberculate fruit.* 



Fraxseria texuifolia, var. tripinxatifida^ Gray^ I. c. Common from Texas to Sonora. This 

 is both Ambrosia fruticosa (excl. var. ^9) and A. confertiflora of De Candolle ; but none of the 

 forms in Berlandier's collection are at all shrubby. 



Franseria Hookeriana, Nutt. El Paso to Sonora, etc.; common. 



Franseria dumosa, Gray^ in Fremont^ 2d Exped. p. 316; var. ALBrcAULis .F. albicaulis, Torr. 

 PL Frem. p, 16. Desert of the Colorado of the West ; common ; Thurher, Bigeloio^ ScJiotf. 



Franseria beltoidea, Torr. PL Fremont^ p. 15. Valley of the Gila; Parry. A well-marked 

 species ; but it should be compared with F. chenopodifolia, Benfh. Bot. Voy. Sulph., from lower 

 California. 



rt 



It 



^The MIowing is an nndescribed species, occurring in Berlandier's reliquuE: 



Ambrosia cheiraxthifolia, (sp. nov.): bumilis, pube minuta canescens; ramis foliosis ; foliis oblongo-Ianceolatis sen 



oblongo-spathulatis integerrimis sessilibus, superioribus flores foemineos fulcrantibua ; capitulis nuisculls elongato-raccmosis 

 ebracteatis: fructibus 4-5-spinosis, spinis crassis.— Saa Fernando, Cohahuila, 1513, 30i3. — A perennial herb, apparently 

 not over a foot in height, considerably branched. Leaves an Inch or rather more in length, 3 to 6 lines wide, all undividtd 

 and entire, whitened both sides with a fine and short appressed pubescence. Sterile heads 2^ lines long, nearly glabrous, 

 aimed with four or five short and stont spines, which are about the length of the similar beak. 



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