Receptacle naked. Leaves alternate, dissected 61 Receptacle bearing chaff among the flowers 59, 64 Pappus of 2 or few awns or teeth 53, 57, barbed in 55, 56 Pappus none, or a mere crown-like margin to the fruit 36, 68, 71 [*] 2. Flowers of two kinds in the same head. Marginal flowers neutral and sterile, either conspicuous or inconspicuous 82 Marginal flowers pistillate and fertile. Receptacle elongated and bearing broad chaff among the flowers 29, 30 Receptacle convex, chaffy. Achene flat, 2-awned 52 Receptacle naked or bearing no conspicuous chaff. Pappus of capillary bristles. Involucre imbricated 28, 32, 33 Pappus of capillary bristles. Involucre merely one row of scales 26, 73, 77 Pappus a short crown or none. Achenes becoming much longer than the involucre 34 Achenes not exceeding the involucre 42, 70, 71 [*] 3. Flowers of two kinds in separate heads, the one pistillate, the other staminate. Heads diœcious; in both kinds many-flowered. Pappus capillary 27, 31, 32, 79 Heads monœcious; the fertile 1--2-flowered and closed. Pappus none 43, 44 § 2. Rays present; i.e. the marginal flowers or some of them with ligulate corollas. [*] 1. Pappus of capillary bristles, at least in the disk. (Rays all pistillate.) Rays occupying several rows 26, 72, 73 Rays in one marginal row, and White, purple or blue, never yellow 17, 24, 25, 26, 73 Yellow, of the same color as the disk. Pappus (at least in the disk) double, the outer short and minute 13, 14 Pappus simple. Scales of the involucre equal and all in one row. Leaves alternate 75 Scales of the involucre in two rows. Leaves opposite 74 Scales of the involucre imbricated. Leaves alternate 10, 11, 15, 17, 35 [*] 2. Pappus a circle of awns or rigid bristles (at least in the disk). Ray yellow, awns few (2--8) 12 Ray rose-color 23 [*] 3. Pappus a circle of chaffy scales, dissected into bristles 65 [*] 4. Pappus a circle of thin chaffy scales or short chaffy bristles. Heads several-flowered. Receptacle chaffy 60 Heads 8--10-flowered. Receptacle naked 18