49. A. ptarmicoìdes, Torr. & Gray. Smooth or roughish; stems clustered (6--20´ high), simple; _leaves linear-lanceolate, acute, rigid_, entire, tapering to the base, 1--3-nerved, with rough margins (2--4´ long); _heads small, in a flat corymb_; scales imbricated in 3 or 4 rows, short; _rays white_ (2--4´´ long).--Dry rocks, W. New Eng. to Minn., along the Great Lakes, and northward. Aug.--Var. LUTÉSCENS, Gray; rays small, pale yellow.--N. Ill. to Sask. 50. A. acuminàtus, Michx. Somewhat hairy; stem (about 1° high) simple, zigzag, panicled-corymbose at the summit; peduncles slender; _leaves oblong-lanceolate, conspicuously pointed, coarsely toothed_ above, wedge-form and entire at the base; involucral scales few and loosely imbricated, linear-lanceolate, pointed, thin (3--5´´ long); heads few or several; rays 12--18, white, or slightly purple.--Cool rich woods; S. Lab. to Penn., and southward along the Alleghanies. Aug.--There is a depauperate narrow-leaved variety on the White Mountains. A monstrous form occurs in Maine, having a chaffy receptacle and the flowers turned to tufts of chaffy paleæ. 51. A. nemoràlis, Ait. Minutely roughish-pubescent; stem slender, simple or corymbose at the summit, very leafy (1--2° high); _leaves_ small (1--1½´ long), rather _rigid, lanceolate_, nearly _entire, with revolute margins_; scales of the inversely conical involucre narrowly linear-lanceolate, the outer passing into awl-shaped bracts; rays lilac-purple, elongated.--Bogs and swamps, N. J. to Newf. and Hudson's Bay. Sept. 52. A. tenuifòlius, L. Very glabrous; stem often zigzag, simple or forked, 6´--2° high; heads rather large, terminal; _leaves few, long-linear, tapering to both ends, rather thick and fleshy, entire_, the upper subulate, pointed; involucre top-shaped, the scales subulate-lanceolate with attenuate acute points; rays large, numerous, pale purple. (A. flexuosus, _Nutt._)--Salt marshes, Mass. to Fla. Sept. § 7. OXYTRIPÒLIUM. _Involucre as in § 6; pappus simple, fine and soft; glabrous annuals, bearing numerous small heads and with narrow entire leaves._ 53. A. subulàtus, Michx. Stem 6--24´ high; leaves linear-lanceolate, pointed, flat, on the branches awl-shaped; scales of the oblong involucre linear-awl-shaped, in few rows; rays somewhat in two rows, short, not projecting beyond the disk, more numerous than the disk-flowers, purplish. (A. linifolius, of previous ed.)--Salt marshes on the coast, Maine to Va. Aug.--Oct. § 8. CONYZÓPSIS. _Scales of the campanulate involucre in 2 or 3 rows, nearly equal, linear, the outer foliaceous and loose; pappus copious, very soft; rays very short or without ligules; low annuals with numerous rather small heads._ 54. A. angústus, Torr. & Gray. Branching, 6--20´ high, nearly glabrous; leaves linear, entire, more or less short-ciliate; ray-flowers reduced to a tube much shorter than the elongated style.--Minn. to Sask. and westward, spreading east to Chicago, etc. (Siberia.)