cles or horns in a single series, 1-flowered. Corolla none. Stamens none.
Branches of the style filiform, elongated. Achenium ovoid or obovoid.—
Herbaceous or rarely sufifrutescent weed-like plants (chiefly American), with
opposite or alternate mostly lobed leaves. Branches terminating in racemes
or spikes, which are simple and sterile above. Sterile heads ebracteate.
Fertile heads clustered at the base of the sterile spikes and bracteate, or sessile
in the axils of the upper leaves. Corolla whitish.
Lessing, De Candolle &c. distinguish Franseria from Ambrosia by the chaffy receptacle
of the sterile flowers, the presence of an abortive style, and the echinate fertile
involucre as in Xanthium, which moreover m Franseria proper (§ X a ^ to p sis
DC 1 is said to be 2-4-celled: but that genus must depend upon the latter characters
alone (at least so far as the section Centroleena is concerned, of which only weJaave
seen specimens); for all the species of Ambrosia we have examined have a sterile
style, and all but A. trifida and A. artemisisefolia exhibit the same,ch!f l r „
as in Franseria. In the Mexican A. fruticosa var. canescens, Bentli. pi. Harbw., the
chaffy scales are conspicuously dilated at the summit. No one appears to remarked
the setiform indexed appendage of the anthers m these plants.—A. bidentata,
Michx. might perhaps be properly separated from the genus.
§ 1. Sterile heads more or less pedicellate; the involucre regular, with the
margin crenate <rr nearly entire: fruit (fertile involucre) subglobose or obovoid.—
E uambrosia.
* Involucre of the sterile heads Cribbed: receptacle naked: fertile heads glomerate at
the base of the sterile spidform racemes; the clusters somewhat invoVwcrate: leaves opposite,
undivided or palmately 3—o-lobed.
1 A . trifida (Linn.): stem tall and stout, hairy, rough; leaves scabrous
and hairy, deeply 3-lobed; the lobes oval-lanceolate, acuminate, serrate;
the lower leaves often 5-lobed ; petioles narrowly winged, ciliate ; racemes
often paniculate; fruit (fertile involucre) turbmate-obovoid, with a short
conical pointed apex, 6-ribbed, the ribs terminating m as many cristate tubercles—
Linn.! spec. 2. p. 987 ; Michx. ! ft. 2. p. 183; Willd.. spec. 4. p.
375; Pursh, fl. 2. p. 581; Ell. ! sk. 2. p. 4761 D C .! prodr. 5. p. 527 ,
Darlingt. fi. Cest. p. 479 ; Hook. fl. Bar.-Am. 2. p. 26. A. Yirgimana &c.,
Moris, hist. 3. sect. 6. t. 1 »ƒ• 4. .
p. integrifolia: leaves ovate or oval-oblong, acuminate, sometimes the upper,
and often the lower ones 3-lobed— A. integrifolia, Muhl. m Willd.. 1.
c.; Pursh. fi. 2. p. 580 ; PC. 1. c. . T • •
Low grounds and along streams, Canada ! to Georgia . and west to Louisiana
and Arkansas ! Aug.-Sept— © Stem 4-sided, 4-9 feet high (sometimes
20 feet or more ! according to Dr. Boykin), branching above. Leaves
large. Involucre of the sterile heads with 3 strong dark purple radiat e nbs,
occupying the side farthest from the axis of the raceme. Corolla greenish-
white, cyathiform-campanulate, scarcely attenuate at the base. Fruit 3-
lines long.—A.coarse unsightly plant.
* * Involucre of the sterile heads not ribbed: receptacle usually chaffy; the chaff filiform.,
or rarely dilated at the summit, rather shorter than the corolla: fertile heads solitary
or glomerate towards the base of the sterile spikes or racemes, or in the axils of the upper
leaves; the dusters somewhat involucrate: leaves l-%pinnalekj cleft or parted, alternate,
the lower opposite.
2. A . crithmifolia (DC.): suffruticose and prostrate at the base; the flowering
stems erect or ascending, velvety-hirsute at the summit; leaves nearly
all opposite, petioled, rather thick, hipinnatifid, when young hirsute-tomen-
tose on both sides ; spikes few, the terminal one much longest; receptacle of
the sterile flowers chaffy; fruit (fertile involucre) obovoid, villous when
young, unarmed.—DC.! prodr. 5. p. 525.
Sea-shore, Key West, Mr. Bennett! Mr. Blodgett!—Whole plant somewhat
hirsute-canescent, 12-15 inches high. Lower leaves hipinnatifid ; the
ultimate segments short; the uppermost occasionally alternate, often simply
pinnatifid; the segments linear, entire or 1—2-toothed. Fertile involucre
with about 4 obscure inflexed teeth near the summit.
3. A. artemisicefolia (Linn.): annual; stem sparsely or rather densely
vilfous, or pubescent, paniculately branched ; leaves hipinnatifid, minutely
strigose-pnbescent, almost glabrous above, paler and frequently somewhat
canescent beneath; the uppermost simply pinnatifid; the lower opposite ;
petioles ciliate or hirsute; racemes spicate, paniculate; receptacle of the
sterile flowers naked ; fertile heads solitary or glomerate along the lower part
of the racemes and bracteate, or in the axils of the upper leaves ; fruit obovoid
or subglobose, nearly glabrous, pointed, armed with about 6 short acute
spines or teeth.—Linn.! spec. 2. p. 988; Lam. ill. t. 765, ƒ. 1; W illd .!
spec. 4. p. 376; Ell. sk. 2. p. 477 ; DC .! prodr. 5. p . 526. A. elatior,
Linn. ! 1. c .; Willd. ! 1. c .; Pursh! fl. 2. p. 581; Ell. 1. c .; Bigel. Jl.
Bost. ed. 2. p. 343 ; Hook. ! jl. Bor.-Am. 1. p. 309; Darlingt. fi. Cest. p.
479; DC. ! 1. c. A. absynthifolia, Michx.! fl. 2. p. 183.
/?. cauline leaves 1-2-pinnatifid ; those of the branches nearly sessile; the
uppermost lanceolate, undivided, or somewhat lobed at the base.—A. hetero-
phylla, Muhl. in W illd .! spec. 4. p. 378; Pursh, l. c .; DC. 1. c.
y. fertile heads glomerate in the axils of the leaves and on short axillary
branchlets or spikes, and more or less racemose or paniculate; the sterile
racemes very short.
d. less pubescent; fruit (usually rather smaller) with the spines or^teeth
very short or obsolete.—A. paniculata, Michx.! fl. 2. p. 183 ; Willd. !
1. c .; Ell. 1. c .; D C .! 1. c .: Hook. 1. c. partly? Iva monophylla, Walt. !
Car. p. 232.
Dry fields and pastures, roadsides, and waste places, Canada ! to Florida!
Louisiana! and Texas! often a troublesome weed in cultivated grounds.
(California, ex Hook. Am . bot. Beechey.) July-Sept.—Stem 1-3 or 4
feet high, at length much branched ; the plant variable as to pubescence, &c.
Fruit a line to a line and a half in length ; the spines or teeth certainly variable,
and sometimes inconspicuous or almost none.—Of the two Linn®an
names, the one we have preferred is the most appropriate.—Bitter-weed.
Rag-weed. Hog-weed.
4. A. coronopifolia : annual ? caneseent-strigose, at length much branched,
leaves crowded, rigid; the upper lanceolate or oblong-lanceolate, sessile;
deeply and somewhat remotely pinnatifid or incised; the lower opposite and
somewhat hipinnatifid, on short margined petioles; sterile heads in loose
spicate racemes, the receptacle chaffy ; fertile heads solitary or somewhat
clustered at the base of the sterile spikes and in the axils of the upper leaves;
fruit globose-ovoid, turgid, unarmed, obtusely pointed, hairy.—A. hispida,
Torr. 1 in ann. lyc. New York, 2. p. 216, doubtless not of Pursh.
Prairies of Illinois! Missouri, (north to Devil’s Lake, Mr. Nicollet!)
Louisiana! and Texas! Aug.-Sept.—Stem erect, 1-5 feet high, often rough
or almost hispid. Leaves very numerous, sometimes nearly all opposite,
2-5 inches long, clothed with very closely appressed hairs, both sides more
or less canescent when young, sprinkled with minute resinous globules; the
segments rather distant, spreading, oblong or lanceolate. Sterile racemes or
spikes proportionally shorter than in the preceding; the heads scarcely