250 COMPOSITE. (composite family.) 



late and fertile ; the disk-flowers staminate with imperfect styles, sterile. Invo- 

 lucre hemispherical, of 2 ranks of short ovate or roundish scales. Keceptacle 

 conical, chaffy. Achenia only in the ray, obcompressed, surrounded by a slen- 

 der callous margin, crowned with the persistent ray-corolla and a pappus of 2 

 small chaffy scales. — Leaves alternate. Heads small, corymbed ; the flowers 

 whitish. (An ancient name of some plant, from 7rapdevos, virgin.) 



1. P. integrifblium, L. Rough-pubescent perennial (l°-3° high); 

 leaves oblong or ovate, crenate-toothed, or the lower (3'- 6' long) cut-lobed be- 

 low the middle; heads many in a very dense flat corymb. —Dry soil, Maryland 

 to Wisconsin and southward. June -Aug. 



2 9. I V A , L. Marsh Elder. Highwater-shrub. 



Heads several-flowered, not radiate ; the pistillate fertile and the staminate 

 sterile flowers in the same heads, the former few (1-5) and marginal, with a 

 small tubular or no corolla ; the latter with a funnel-form 5-toothed corolla. 

 Anthers nearly separate. Scales of the involucre few, roundish. Receptacle 

 small, with narrow chaff among the flowers. Achenia obovoid or lenticular. 

 Pappus none. — Herbaceous or shrubby coarse plants, with thickish leaves, the 

 lower opposite, and small greenish-white heads of flowers ; in summer and au- 

 tumn. (Name of unknown derivation.) 



§ 1. Fertile flowers with a small tubular corolla: involucre simple (heads nodding in 

 the axils of leaf-like bracts, forming spikes or racemes). 



1. I. frutescens, L. Shrubby at the base, neurit/ smooth (3° -8° high); 

 leaves oval or lanceolate, coarsely and sharply toothed, rather fleshy, the upper 

 reduced to linear bracts, in the axils of which the heads are disposed, in leafy 

 panicled racemes ; fertile flowers and scales of the involucre 5. — Salt marshes, 

 coast of Massachusetts to Virginia, and southward. 



2. I. ciliata, Willd. Annual (2° -8° high), rough and hairy ; leaves ovate, 

 pointed, coarsely toothed, downy beneath, on slender ciliate petioles ; heads in dense 

 spikes, with conspicuous ovate-lanceolate rough-ciliate bracts ; scales of the in- 

 volucre and fertile flowers 3-5. — Moist ground, from Illinois southward. 



§ 2. EUPHR6SYNE, DC. Fertile flowers 5, in the axils of as many thin mem- 

 branaceous scales of the involucre, which loosely enwrap the achenia, their corolla 

 a mere rudimentary ring or none. 



3. I. xanthiif61ia, Nutt. Animal, tall, rbughlshj leaves nearly all oppo- 

 site, hoary with minute down, ovate, rhombic, or the lowest heart-shaped, doubly 

 or cut-toothed, or obscurely lobed ; heads small, crowded in spikes or clusters 

 disposed in axillary and terminal panicles; bracts inconspicuous. — N. W. Wis- 

 consin (T. J. Hide), and northwestward. 



30. AMBROSIA, Tourn. Ragweed. 



Sterile and fertile flowers occupying different heads on the same plant; the 

 fertile 1 - 3 together and sessile in the axil of leaves or bracts, at the base of the 

 racemes or spikes of sterile heads. Sterile involucres flattish or top-shaped, 

 composed of 7 - 12 scales united into a cup, containing 5-20 funnel-form stum- 



