288 COMPOSITE. IvA.
habit of Glaux maritima. Leaves about an inch long, varying from 2 lines
to half an inch in breadth, pale; the close strigose pubescence (traces of
which are almost always visible with a lens) scarcely perceptible to the
naked eye except on the margins. The involucral scales are sometimes
nearly or quite distinct (I. axillaris, Nutt. 1. c. excluding the reference to
Hooker); sometimes variably united, as described and figured by Hooker,
when it is the I. foliolosa, Nutt. 1. c. But Mr. Nicollet’s specimens from the
Missouri (in which the leaves are as evidently 3-nerved and hairy as in any
state of the species,) have the scales in some instances united to the middle,
while more commonly they are nearly distinct.
4. 1. microcephala (N u tt.): stem slender, glabrous, virgately branched;
heads very small, nearly sessile in the axils of the narrowly linear and fleshy
sessile entire alternate leaves, nodding; scales of the involucre 4-5, distinct;
flowers about 6, three of them pistillate.—Nutt. ! in trans. Amer. phil. soc. 1. c.
Florida, Dr. Baldwin!—Leaves about half an inch long and half a line
wid e : the capitula not larger than an ordinary pin’s head. Nutt.
§ 2. Scales of the many-flowered involucre 6-9, imbricated in 2-4 series.
5. I. imbricata (Walt.): perennial, herbaceous or nearly so, mostly glabrous
; branches ascending; leaves commonly alternate, fleshy, lanceolate,
mucronulate, tapering to the base, sessile, obscurely 3-nerved, entire or denticulate
serrate ; heads solitary or in pairs in the axils of the upper leaves, on
short pedicels, forming foliaceous spikes or racemes; exterior scales of the
involucre orbicular, fleshy, with a narrow scarious margin; the interior ob-
ovate, the scarious margin lacerate-denticulate; fertile flowers 2-4; chaff of
the receptacle linear-spatulate, denticulate at the summit.— Walt.! Car. p.
232; Michx.! fl. 2. p. 184; Pursh! fl. 2. p. 580; E ll.! sic. 2. p. 475;
DC. ! prodr. 5. p. 530.
Sandy sea-shore,. N. Carolina! to Florida! and Louisiana! Also Key
West, Mr. Blodgett! July-Oct.—Plant 1-2 feet high, suffrutescent at the
base. Leaves about an inch long. Corolla of the fertile flowers very small
and short, 5-parted or irregularly cleft. Fertile style divided nearly or quite
to the base; the branches linear, rather obtuse, one of them sometimes abortive.
Sterile flowers numerous. Achenia slightly compressed.—“ Leaves
of the 'fertile branches linear; of the barren ones cuneate-obovate and serrate
toothed: the plant has an extremely strong odor of honey.” M. A .
Curtis, mss.
§ 3. Involucre turbinate, composed of 3 scales united nearly to the summit,
3-6-flowered, the fertile, flowers solitary.—Monachsena.
6. I. angustifolia (Nutt.): annual, strigose-pubescent: stem erect or decumbent
at the base, much branched; leaves narrowly linear or lanceolate-
linear, 1-3-nerved, tapering at the base or somewhat petioled, entire, the
lower often denticulate; beads (small) subsessile, deflexed, forming narrow
virgate leafy spikes; chaff of the receptacle filiform, minute.—Nu tt.! in
DC. prodr. 5. p. 529, Sfin trans. Amer. phil. soc. 1. c.
Prairies, Arkansas, Nuttall! Dr. Leavenworth! Western Louisiana, Dr.
Hale ! Texas, Drummond ! Dr. Leavenworth ! Aug.-Sept.—Stem 1-3
feet high. Leaves &c. minutely pubescent and somewhat canescent with
appressed strigose hairs ; the lower 1-2 inches long and 1-3 lines wide; the
upper much narrower; the bracteal ones almost setaceous. Spikes very numerous,
4-6 inches long. Heads scarcely more than a line in'lengfh, frequently
with only 3 flowers, two of them staminate. Sterile style abor-
IVA. COMPOSITE. 289
five, short, glabrous, not thickened at the summit. Achenium somewhat
compressed.
79. PICROTHAMNUS. Nutt, in trans. Amer. phil. soc. (n. ser.) 7. p. 417.
Fertile and sterile flowers in the same heads; the former 3-5, marginal,
with a very small obliquely truncate and obscurely 2-3-toothed corolla ; the
latter about 10, with an infundibuliform 5-toothed corolla, inflated at the summit.
Scales of the depressed-hemispherical involucre about 5, orbicular,
distinct. Receptacle flat, naked. Sterile flowers destitute of ovaries; the
anthers slightly united, tipped with an inflexed mucronate appendage; the
abortive style entire, with a radiate-penicillate summit. Style in the fertile
flowers deeply 2-cleft; the branches subulate-linear, glabrous. Achenia
obovoid-oblong, terete, entirely clothed, as well as their corollas, and the
tube of the sterile corolla, with very long and tortuous woolly hairs.—A low
rigid suffruticose plant, with the habit of Artemisia, canescently pubescent,
much branched; the branches spinescent. Leaves small, alternate or
crowded, petioled, pedately or 2-ternately divided. Heads small, in short
and somewhat loose racemes or spikes; the raehis persistent and spinescent.
Flowers pale yellow.
P . desertorum (Nutt.! 1. c.)
Arid deserts in the Rocky Mountains, towards the north sources of the
Platte, Nuttall!—Plant bitter to the taste (whence the name), 4-18 inches
high.—Mr. Nuttall doubtfully refers it to Millerieae, next to Clibadium : but
the heads and flowers entirely accord with Iva, except in the naked receptacle,
and the woolly hairs of the achenia and corolla.
Div. 5. A i b r o s i e -®, DC.—Fertile and sterile flowers in different
heads on the same individual; the former (1-4) often apetalous ; the latter
tubular. Scales of the involucre in the fertile heads united into an ovate or
oblong persistent covering, including or closely investing the flowers and fruit,
often prickly or spinose. Pappus none. Anthers approximate, but distinct
or very slightly united : filaments inserted at the base of the corolla.
80. AMBROSIA. Tourn.; Linn.; Gcertn.fr. t. 164; Schlcuhr, handb. t.
292 ; DC. prodr. 5. p. 524.
Sterile heads occupying the upper portion, the fertile at the base of the racemes
or spikes, or in the axils of the upper leaves. S t erile F l . Involucre
flattish, hemispherical, or somewhat turbinate, composed of 7-12 united
scales, 5-20-flowered. Receptacle flattish, naked, or usually with filiform
chaff among the flowers. Corolla infundibuliform or turbinate, 5-toothed.
Anthers tipped with a mucronate-setigerous inflexed appendage. Ovary
none or rudimentary : abortive style included, minutely fimbriate or radiate-
penicillate at the summit. F ertil e F l . Involucre globose-ovoid, oblong,
or turbinate, closed, pointed, usually armed near the summit with 4-8 tuber-
vol. ii.—37