A MBROSIA CEA E. 909 



Receptacle chaffy, the linear or spatulate chaff enveloping the flowers. Marginal 

 flowers 1-6, pistillate, fertile, their ccrollas short, tubular or none. Disk-flowers 

 perfect, sterile, their corollas ftmnelform, 5-lobed, their styles undivided, dilated at 

 the apex. Anthers entire at the base, yellow, scarcely coherent with each other, 

 tipped with mucronate appendages. Achenes compressed, obovoid, glabrous. 

 Pappus none. [Nam.d alter Ajuga Iva, from its similar smell.] About 12 spe- 

 cies, natives of America. Besides the following, 6 others occur in the southern 

 and western U. S. 



Meads spicate or racemose, solitary-axillary, each subtended by a linear or oblong leaf. 

 Heads solitary, pedicelled. 



Bracts of the involucre 4-5; heads 3-5 mm. high. 



Leaves serrate, oval or oblong ; eastern. i. I.frutescens. 



Leaves entire or nearly so, obovate or oblong; western. 



2. /. axillaris. 

 Bracts of the involucre 6-9 ; heads 6-8 mm. high ; southeastern. 



3. I. imbricata. 

 Heads spicate; leaves dentate. 4. /. ciliata. 



Heads spicate-paniculate, not subtended by leaves. 5. /. xanthiifolia. 



1. Iva frutescens L. MARSH ELDER. HIGH-WATER SHRUB. (I. F. f. 3586.) 

 Perennial, shrubby or herbaceous, somewhat fleshy; stem minutely pubescent, or 

 sometimes glabrous below, 9-35 dm. high. Leaves oval, oblong, or oblong-lanceo- 

 late, all the lower ones opposite, short-petioled, 3-nerved, acute or obtusish, serrate, 

 narrowed at the base, the lower 10-15 cm. long, 3-5 cm. wide, the upper smaller 

 and narrower, passing gradually into those of the racemose inflorescence, which are 

 much longer than the short-pedicelled heads ; involucre depressed-hemispheric, its 

 bracts orbicular-obovate, separate; fertile flowers about 5, their corollas tubular. 

 Along salt marshes and on muddy seashores, N. H. to Fla. and Tex. July-Sept. 



2. Iva axillaris Pursh. SMALL- FLOWERED MARSH ELDER. (I. F. f. 3587.) 

 Perennial by woody roots; stems herbaceous, ascending, glabrous or sparingly 

 pubescent, simple or branched, 3-6 dm. high. Leaves sessile, entire or very nearly 

 so, obtuse, faintly 3 nerved, obovate, oblong, or linear-oblong, 1-4 cm. long, thick, 

 somewhat fleshy, glabrous or pubescent, the lower opposite, the upper alternate 

 and smaller, passing gradually into those of the inflorescence; heads mostly solitary 

 in the axils of the leaves, 4-6 mm. broad, short-peduncled ; involucre hemispheric, 

 about 3 mm. high, its bracts about 5, connate at the base; pistillate flowers 4 or 5, 

 their corollas tubular. In saline or alkaline soil, N. W. Terr, to S. Dak., Neb., 

 N. Mex., Br. Col. and Cal. May-Sept. 



3. Iva imbricata Walt. SEACOAST MARSH ELDER. (I. F. f. 3588.) Peren- 

 nial by woody roots, glabrous or nearly so throughout, fleshy; stem 3-6 dm. high, 

 simple, or sparingly branched. Leaves all but the lowest alternate, sessile, oblong- 

 spatulate, or lanceolate, obtusish, mucronulate, entire, or rarely serrate, obscurely 

 3-nerved, the larger 3-5 cm. long. 6-10 mm. wide; heads short peduncled or nearly 

 sessile, the upper ones longer than their subtending leaves; involucre broadly cam- 

 panulate, its bracts 6-9, not united, somewhat imbricated in 2 series; fertile flowers 

 2-4, their corollas tubular, the staminate ones much more numerous. On sandy 

 seashores, Va. and N. Car. to Fla. and La. July-Oct. 



4. Iva ciliata Willd. ROUGH MARSH ELDER. (I. F. f. 3589.) Annual, 

 hispid- pubescent; stem simple, or branched, 6 20 dm. high. Leaves nearly all 

 opposite, ovate, petioled, scarcely fleshy, puberulent beneath, acuminate at the 

 apex, abruptly or gradually narrowed at the base, coarsely and irregularly dentate, 

 3 nerved, the lower 10-12 cm. long; upper leaves linear-lanceolate, hispid, squar- 

 rose, much longer than the heads; heads about 2 mm. broad; bracts of the involucre 

 3-5, distinct or united below; hispid; fertile flowers 3-5, their corollas slender; 

 staminate flowers 10-15. ^ n m ist soil. 111. to Neb., La. and N. Mex. Aug.-Oct. 



5. Iva xanthiifolia (Fresen.) Nutt. BURWEED MARSH ELDER. (I. F. 

 f. 3590.) Annual; stem much branched, pubescent or puberulent above, glabrous 

 below, 1-2 m. high. Leaves nearly all opposite, broadly ovate, long-petioled, 

 acuminate at the apex, abruptly or gradually contracted at the base, coarsely and 

 irregularly dentate, pale and canescent or puberulent beneath, roughish above, 3- 

 ribbed; inflorescence spicate-paniculate. terminal and axillary, ample, naked; heads 

 sessile or minutely peduncled, less than 2 mm, broad; bracts of the involucre in 2 



