AMBROSIACEAE 1151 
above, petioled, the lower 2-pinnatifid, the upper 1-pinnatifid, the segments often toothed, 
acute or acuminate: racemes of staminate heads several or numerous, 5-18 em. long ; in- 
volucre 3.5—5 mm. broad, pubescent: pistillate heads mostly solitary : fruit 3-4 mm. long, 
with an abrupt tip and 4 short tubercles, or these wanting. 
On moist prairies, the Northwest Territory to Illinois, Texas, Mexico and California. 
4. IVA L. 
Annual or perennial herbs, or shrubby plants, with glabrous or coarsely pubescent 
foliage. Leaves opposite, or alternate above: blades narrow or broad, entire or toothed, 
often fleshy. Heads solitary or variously disposed. Involucre campanulate, hemispheric 
or cup-shaped : bracts few, distinct or partially united. Receptacle bearing with linear 
or spatulate chaff. Flowers inconspicuous, the marginal 1-6, pistillate, fructiferous, with 
tubular or obsolete corollas: disk-corollas perfect, not fruit-producing: corolla normal : 
tube funnelform ; lobes 5; stigmas simple, dilated above. Anthers entire at the base, with 
mucronate appendages. Achene broadest above the middle, without pappus. MarsH 
ELDER. 
Heads subtended by bracts similar to the leaves or conspicuous bracts. 
Involucres peduncled. s 
Leaf-blades entire : involucre with 6-9 bracts. 
Leaf-blades glabrous, 2-5 em. long: involucres 4-5 mm. high. 1. I. imbricata. 
Leaf-blades strigose, 8-15 mm. long: involucres about 2 mm. high. 2. I. asperifolia. 
Leaf-blades toothed : involucre with 4-5 bracts. 3. I. frutescens. 
Involucres sessile. 
Bracts subtending the heads ovate-lanceolate or rhomboidal. 4. I. ciliata. 
Bracts subtending the heads linear or nearly so. 
Leaf-blades ovate or elliptic. 5. I. caudata. 
Leaf-blades linear or nearly so, or linear-filiform. 
Foliage glabrous or nearly so: fructiferous flowers 3. 6. I. microcephala. 
Foliage strigose-hirsute or hirsute: fructiferous flower 1. 7. I. angustifolia. 
Heads subtended by inconspicuous bracts or naked. 8. 1. xanthiifolia. 
1. Iva imbricàta Walt. Perennial, smooth and glabrous, the foliage honey-scented. 
Stems erect or decumbent, 3-7 dm. long, branching: leaves fleshy, numerous, mostly 
alternate ; blades narrowly linear-subulate to linear, 2-5 cm. long, acute, entire or barely 
repand, sessile: heads drooping, short-peduncled, subtended by linear bracts : involucre 
campanulate, 4-5 mm. high: bracts suborbicular or oblong-orbicular, obtuse or retuse: 
corolla 4-5 mm. long, sparingly glandular ; lobes ovate, acute, recurved : achenes 2 mm. long. 
In sand on the coast, Virginia to Florida and Louisiana. Summer and fall. 
2. Iva asperifdlia Less. Stem 2-4 dm. tall, simple or sparingly branched: leaves 
opposite on the lower part of the stem ; blades mainly linear-lanceolate, 8-15 mm. long, 
acute, entire, strigose, narrow to the base : spikes slender : heads drooping, surpassed by the 
subtending bracts : involucre somewhat 3-angled, obpyramidal, about 2 mm. high. 
In waste places, near Pensacola, Florida. Native of Mexico. Spring to fall. 
3. Iva frutéscens L. Perennial, shrubby or herbaceous. Stems erect, 1-3.5 m. 
tall, branching, minutely pubescent or puberulent: leaves mainly opposite, often pubescent 
like the stem ; blades ovate to linear, 5-10 cm. long, acute, serrate, acuminate to cuneate 
at the base, short-petioled : bracts narrowly linear, usually surpassing the heads: heads 
drooping, short-peduncled: involucre campanulate, 3-3.5 mm. high, often broader than 
high ; bracts orbicular to orbicular-cuneate, obtuse: corolla funnelform or in the fruit- 
ee flowers tubular, 2-2.5 mm. long ; lobes ovate, acute: achenes broadly cuneate- 
obovate. 
On beaches and brackish shores, Massachusetts to Florida and Texas. Summer and fall. 
4. Iva ciliàta Willd. Annual, strigose-hispid or hispidulous. Stems erect, 5-18 
dm. tall, simple or branching, commonly mottled: leaves opposite or nearly so; blades 
ovate, elliptic or oval, 4-10 cm. long, acuminate, serrate, narrowed into short petioles : 
spikes 3-20 cm. long, usually continuous: bracts ovate-lanceolate to rhomboidal, acumi- 
nate, ciliate: heads drooping : bracts of the involucre 3-5, obovate to suborbicular, some- 
times broader than high, about 2 mm. long: staminate flowers 10-15: fructiferous flowers 
3-5 : corolla 1.5-2 mm. long : achenes 3 mm. long. 
In moist soil, Nebraska to Louisiana, Texas and New Mexico. Summer. 
5. Iva caudata Small Annual, hispid or somewhat strigose. Stems erect, 4-10 
dm. tall, branching, ridged: leaves opposite or nearly so; blades ovate or elliptic, 4-10 
cm. long, coarsely and irregularly serrate or incised, acuminate, acute to truncate at the 
base; petioles 1-1 as long as the blades, bristly : spikes continuous or interrupted below, 
conspicuously bracted : bracts linear or with a narrowly elliptic base and linear tip, 7-15 
