1298 AMBROSIACEAE 
or 5—9 in I. imbricata. Receptacle with large bractlets. Corolla of the pistil- 
late flowers a truncate tube. Achenes nd flattened, usually obovoid.— 
About 20 species, Àmerican.—MARSH-ELDE 
Plants p heads mostly peduncled: bracts of the involucre’ 5-9, or rarely 4. 
Bracts of ER involucre 6-9, imbricate in two series: leaf- 
blades e 1. I. imbricata. 
Bracts of is es olucre 5 or rarely 4, in one series and only 
slightly overlapping: i es toothed. 2. I. frutescens. 
Plants ee heads sessile: bracts of the involucre 3, or 
rarely or 
Leaf-blades broad, coarsely toothed, petioled: those of the 
inflorescence different, Eoi. 
Leaves of the inflorescence with ovate to lanceolate 
Short-acuminate blades. 
Leaves of the inflorescence with linear or linear-lanceo- 
late caudate-acuminate blades 4, I. caudata. 
Leaf-blades narrow, entire or shallowly toothed, sessile or 
are -petioled ; those of the e nearly similar, 
Bracts of the involucre distinct: stam and pistillate 
Fen three each: leaf-blades lin 5. I. microcephala. 
Bracts of the involucre partly Suited: ' pistillate flowers 
usually solitary : leaf-blades oblong 6. I. asperifolia. 
I. ciliata. 
e 
I. imbricata Walt. Perennial with a woody base: stem 1 m. tall or less, 
smooth and glabrous: leaf-blades linear i linear- ‘elliptic, linear-oblanceolate, or 
u 
Or 
achenes 3-3.5 mm. long. Fia sand- ade 
m rocky shores Fla. to and 
. I.)—Sum.—f all. 
2. frutescens [M pe pee with a 
ance base: stem 3.5 r less, pubes 
cent, at least do pues ‘blades elliptic, 
linear aren, e Rd or nearly 
lin above, 4—10 long, d 
coarsely serrate: involueres 3. aos . high; 
di E val or obo on schenes | p 2. 
mm. meee ELDE IG 
smi). — Salt secum ae muc ouem Plain, Fla. to Tex. and Va.— 
Sum 
| illd. Annual, 1.8 m. x m pos sos piod rough-pubescent: 
ee blades ae oval, or 'elli iptie, 4— ong, short- Eee d 
serrate: hea = con tiguous, subtended by Mond) ciliate pm involueres 3—4 
high, rough-pubescent: achenes colored, about 3 mm. long, with “saint 
fue sae ridges.—Moist soil, various as La. to N. M, 
Nebr., and Ill.; extending as a a weed E to Ala.—Sum.-fall. 
. I. caudata Small Annual, 1 m. tall or alee stem rather sparingly hispidu- 
lous: leaf-blades ovate to elliptic, 4-15 em. long, acuminate, eee d un- 
evenly serrate: cud: contiguous or appr in ate, subtended by coarsely ciliate 
id involueres oe ET pubesce ent: achenes broadly cuneate-obovoid, 3.5 
long, with prom even ridges. cns and low oo yon 
Plain and adj. ee ate, "Miss. € o La., Mo., and Ill.—Sum.-fal 
5. I. microcephala Nutt. Annual, 1 m. tall or less: stem glabrous or minutely 
pubescent ite ally above, often with numerous erect branches: leaf-blades 
narrowly linear, 2-5 em. long, entire or shallowly toothed, glandular-punctate: 
heads con pn ous or nearly so, aa d by subulate or linear-filiform bracts: 
involuere eampanulate, about 2 mm. high; poseen obovate to dee DNE 
