COMPOSITAE. 



VOL. III. 



i. Megalodonta Beckii (Torr.) Greene. 

 Water Marigold. Fig. 4518. 



Bidens Beckii Torr. ; Spreng. Neue Entdeck. 2 : 

 135. 1821. 



M. Beckii Greene, Pittonia 4: 271. 1901. 

 M. nudata Greene, loc. cit. 1901. 



Stems simple, or little branched, 2-8 long. 

 Submersed leaves sessile, i'-2' long, repeat- 

 edly divided into numerous capillary segments ; 

 emersed leaves few, sessile, opposite, or some- 

 times in 3's, lanceolate or oblong, acute, serrate 

 or laciniate, i'-ii' long; heads solitary or few, 

 short-peduncled, i'-ii broad; involucre hemi- 

 spheric, its bracts oval or oblong, obtusish, 

 glabrous, the outer somewhat shorter than the 

 inner; rays 6-10, obovate, or oblong, notched, 

 golden yellow ; achenes nearly terete, s"~7" 

 long; pappus of 3-6 slender awns, downwardly 

 barbed above, smooth below, divergent, 6"-i2 ' 

 long. 



In ponds and streams, Quebec to New Jersey, 

 west to Manitoba and Missouri. Aug.-Sept. 



73. THELESPERMA Less. Linnaea6: 511. 1831. 



Glabrous annual or perennial herbs, with opposite linear and undivided, or finely dis- 

 sected leaves, and long-peduncled heads of both tubular and radiate flowers, or the rays 

 wanting. Involucre hemispheric or campanulate, of 2 distinct series of bracts, the outer 

 short, narrow and somewhat spreading, the inner united nearly to or beyond the middle into 

 a cup, their tips scarious-margined. Receptacle flat, chaffy, the 2-nerved broad white scarious 

 chaff subtending the disk-flowers and .achenes. Ray-flowers, when present, neutral, the rays 

 yellow, entire or toothed. Disk-flowers perfect, fertile, their corolla with a slender tube and 

 5-toothed limb. Anthers obtuse and entire at the base. Style-tips acute. Achenes, some or 

 all of them, papillose on the back, oblong or linear, slightly compressed or terete, wingless. 

 Pappus of 2 retrorsely hispid awns or scales, or sometimes none. [Greek, nipple-seed.] 



About 10 species, natives of the south central United States, Mexico and southern South Amer 

 ica. Type species: Thelesperma scabiousoides Less. 



Rays large ; pappus-awns shorter than the width of the achene. 



Leaves not rigid, their segments filiform-linear ; annual or biennial. i. T. trifidum. 



Leaves rigid, their segments linear; perennial. 2. T. intermedium. 



Rays inconspicuous, or none ; awns longer than the width of the achene ; perennial. 



3. T. gracile. 



i. Thelesperma trifidum (Poir.) Brit- 

 ton. Fine-leaved Thelesperma. 

 Fig- 45I9- 



Coreopsis trifida Poir. in Lam. Encycl. Suppl. 2 : 



353- 1811. 

 Thelesperma filifolium A. Gray, Kew. Journ. Bot. 



i : 252. 1849. 

 Thelesperma trifidum Britton, Trans. N. Y. Acad. 



Sci. 9 : 182. 1890. 



Annual or biennial; stem branched, i-3 

 high. Leaves numerous, not rigid, ii'-2' long, 

 bipinnately divided into filiform or linear- 

 filiform segments; heads several or numerous, 

 i2"-is" broad ; outer bracts of the involucre 

 about 8, subulate-linear, equalling or more 

 than half as long as the inner, which are 

 united not higher than the middle ; rays 6-10, 

 somewhat spatulate, 3-lobed ; disk purple or 

 brown ; achenes linear-oblong, straight, or 

 slightly curved, the outer ones strongly papil- 

 lose; awns of the pappus not longer than the 

 width of the summit of the achene. 



In dry soil, South Dakota, Missouri and Ne- 

 braska to Colorado, Texas, New Mexico and north- 

 ern Mexico. June-Aug. 



