* * Annual. (Ambrosidiura, Nutt.')
5. F. Hookeriana (Nutt.): much branched, paniculate ; stem scabrous and
more or less hirsute leaves bipinnatifid, with few oblong or somewhat linear
segments, strigose-canescent; racemes paniculate; sterile involucres 5-8-
cleft, 10—20-flowered ; the fructiferous involucre covered with (12 or more)
long and slender flatfish spreading spines.—F. Hookeriana & F. montana,
Nutt.! 1. c. Ambrosia acantbicarpa, Hook. ! jl. Bor.-Am. 1. p. 309.
' Saskatchawan to the Oregon River, Douglas ! Drummond! and near the
sources of the Colorado of the West, Nuttall!—Fertile portion of the racemes
often as long as the sterile, frequently leafy at the base and partly compound.
Sterile heads small, on filiform pedicels.
82. XANTHIUM. Tourn. inst. t. 252 ; Linn. ; Gtertn. fr . t. 164 ;
-Schkuhr, handb. t. 291 ; DC. 1. c.
Heads glomerate-spicate ; the spikes sterile at the summit. S t e r i l e F l .
numerous in subglobose heads ; the scales of the involucre distinct, in a single
series. Receptacle oblong or cylindraceous, chaffy. Stamens inserted
in the base of the short and dilated 5-toothed and somewhat hairy corolla:
anthers distinct, but connivent. Style abortive, undivided. F e r t i l e F l . two,
enclosed in a 2-celled ovoid or oblong coriaceous closed involucre, which is
clothed with hooked prickles and terminated by 1 or 2 stout beaks. Corolla
filiform. Stamens none. Branches of the style linear-filiform. Achenia
solitary in each cell of the involucre, oblong, flat.—Coarse annual weeds,
with branching stems, and alternate, petioled, lobed or toothed leaves.
§ 1. Leaves cordate, lobed, incisedj or toothed, with no spines at their base:
fructiferous involucre with 2 beaks.—Euxanthium, DC.
1 . X . strumarium (Linn.) : fructiferous involucre oval, somewhat pubescent
; the beaks straight (appressed or spreading) ; leaves 3-5-lobed incise-
ly-toothed ; the lobes acute.—Linn. spec. (ed. 2) p. 1400 ; Fl. Dan. t. 270 ;
Lam. ill. t. 765, f . 1 ; Engl. bot. t. 2544 ; DC. ! prodr. 5. p. 523.
0. Canadense: fructiferous involucre pubescent-scabrous, or at length
glabrous; the beaks straight or slightly incurved; stem usually spotted.
—X. majus Canadense, Herm. Lugd. p. 635? X. elatius Americanum,
&c., Moris, hist. 3. p. 604. sect. 15. t. 2, f . 2 ? X. Canadense, Mill. diet,
no. 2 ? Hook. 8f Am . bot. Beechey, p. 148. X. Carol, medium, Dill. Elth.
t. 321 ? excl. fig. 13-16. X. Americanum, Walt. Car. p. 231 ? X. macro-
carpon 0. glahratum, DC. 1. c. X. strumarium, Michx. Jl. 2. p. 182 ;
Ell. sk. 2. p. 479 1
Waste places, around barnyards, &c., apparently introduced. Also Key
West, Florida, M r . B lo d g e ttl (with fruit a little smaller than the European
plant, the beaks appressed.) (3. Fields, &c., Canada! Northern and Western
States ! and probably in the Southern States. Also in California, H o o k .
Sf Am . July-Sept.—The true X. strumarium is more or less naturalized ;
the var. [3. is probably indigenous, and perhaps a distinct species; but we
can indicate no further characters to distinguish it, except that the fruit is in
general a little larger than in the European plant, and the leaves perhaps
less lobed.—B u r r-w e e d . Cockle-burr. Clot-burr.
2. X . echinatum (Murray): fructiferous involucre oval, very densely
clothed with rigid slender prickles, which are strongly hispid, as well as the
more or less incurved beaks ; stem and petioles rough and strlgose, spotted ;
leaves scabrous, broadly subcordate, obtuse, irregularly repand-tootbed, obscurely
lobed.—Murr. comm. Gcett. 6 (1783-84) p. 32, t. 4 (good figure);
Willd. spec. 4. p. 374. X. maculatum, Rafi! in S ill jour. 1. p. 151.
X . orientale, Muhl. cat. p. 89 ; Nutt. gen. 2. p. 186 ; Torr. ! cat. pl- N™
York, p. 73 ; not of Linn. X . macrocarpon, DC.! prodr. 5. p. 523, in
p a rt; Beck, bot. p. 210. . ,
0. prickles of the oval-oblong fructiferous involucre stouter and less crowded
; leaves incisely lobed. fijjffliJj', ■ U
Waste places near salt water, Massachusetts ! and New York . to Carolina
1 0. Banks of Spirit Lake, head-waters of the Little Sioux River ot
the Missouri, Mr. Nicollet! Aug.-Oct.—A stout and very coarse plant, 1-2
feet high. Mature fruit about an inch and a quarter long, turgid, three-
fourths to nearly an inch broad, including the slender but rigid recurvedsnreading
prickles with which it is very densely invested, and which, as well
as the beaks, are clothed with rigid bristly hairs. This is certainly different
from the X. macrocarpon, DC., which has an oblong fruit with very stout,
suberect and scattered prickles. Murray’s plant was raised from seeds collected
at New York by Wangenheim. W e have never met with it at a distance
from the sea-coast, except the"specimens of var. 0., which are, however,
from a region which abounds in salt marshes. These indeed approach
X. macrocarpon, and may prove to belong to that species ; but they are apparently
in a stunted state.
§ 2. Leaves narrowed into the petiole, furnished with spines at their base.
fructiferous involucre with a single beak.—Acanthoxanthium, DC.
3. X . spinosum (Linn.) : spines at the base of the leaves 3-parted, slender,
stem much branched ; leaves ovate-lanceolate, cuneate at the base, entire or
somewhat 3-lobed, with the middle lobe prolonged, acuminate, the lower
surface and the veins of the upper canescent; involucre cylindrical-oblong,
with an inconspicuous beak; the prickles slender. Lvnn. spec. (ed. 2) 2.
p. 1400; Lam. ill. t. 655, ƒ. 4 ; Ell. sk. 2. p. 479 | D C .! prodr. 5. p..523.
Naturalized in many places along the coast from Massachusetts ! to Georgia
! Sept.-Nov.—Heads few, or solitary and sessile in the axils, »pines
yellowish.
Subtribe 2. H é l i a n t h e m, Less.—Heads heterogamous and radiate,
rarely homogamous and discoid ; the disk-flowers perfect. Receptacle
chaffy. Lobes of the corolla in the perfect flowers often somewhat thickened
and papillose. Anthers blackish, not caudate at the base. Pappus either
wanting, or coroniform, or of awns which aresometim.es chaffy or with chaffy
scales intermixed, never of capillary bristles, nor of several uniform and distinct
chaffy scales.—Leaves commonly opposite.
CONSPECTUS OF THE GENERA.
Div. 1. H euopsidejE.—Rays fertile, rarely none. Achenia with a thick outer
integument, not obcompressed.
83. M elanthera. Rays none. Pappus of few rigid caducous bristles.
84. Z innia. Rays persistent. Pappus 1-2-awned, persistent.
85. W yethia. Rays numerous. Pappus coroniform-toothed and 1-3-awned.