with it the septum and therefore closed, the other carpel open on the inner face. 

 About 100 species in the warmer parts of America. 



1. Flowers numerous in a dense conspicuous head; corolla 2-3 mm. long, densely 

 white-bearded in the throat; fruit 2-4 mm. long, smooth, capped 

 by sepals 1.5-2 mm. long 1. S. glabra. 



1. Flowers few in inconspicuous heads; corolla less than 2 mm. long, somewhat 

 pubescent at and above the throat; fruit 2-2.5 mm. long, mostly 

 puberulent, capped by sepals 1 mm. long or less 2. 5. tenuior. 



1. Spermacoce glabra Michx. Smooth buttonweed. Fig. 727. 



Glabrous perennial herb; stems simple or unbranched, spreading, 6 dm. long 

 or more; leaves elliptic to oblong-lanceolate or oblanceolate, acute to acuminate 

 at apex, to 8 cm. long; stipular sheaths with several filiform segments 2-3 mm. 

 long; axillary heads many-flowered; corolla 2-3 mm. long, slightly exceeding the 

 calyx, conspicuously white-bearded in the throat, bearing the anthers at its base; 

 filaments and styles short; fruit somewhat turbinate, smooth, 2-4 mm. long, 

 crowned by the conspicuous triangular-lanceolate spreading calyx teeth. 



Damp shores, swamps, edge of lakes, ponds, sloughs and flooded areas, low 

 woodlands and in openings, in the e. third of Tex. and Okla. (LeFlore and Ottawa 

 COS.), May-Oct.; from Fla. to Tex., n. to O., Ind., 111., Mo. and Kan. 



2. Spermacoce tenuior L. Slender buttonweed. 



Annual, glabrous or nearly so; stems simple and erect or more or less diffusely 

 branched from the base, to about 4 dm. long; leaves linear to oblong or oblong- 

 lanceolate, narrowed into short petioles, acute to acuminate at apex, more or less 

 scabrous, 2-5 cm. long; axillary heads with few flowers; calyx teeth subulate to 

 subulate-lanceolate; corolla white, about 1.5 mm. long, funnelform, somewhat 

 pubescent at and above the throat; fruit didymous-obovoid, mostly puberulent or 

 short-pubescent, 2-2.5 mm. long, somewhat crustaceous and crowned with the 

 4 calyx teeth. 



In wettish clay soils along creeks in s. Tex., Sept.-Jan.; also Fla. and La., the 

 W.I. and cont. trop. Am. 



7. Diodia L. Buttonweed 



Spreading, decumbent, prostrate or ascending annual or perennial herbs; leaves 

 opposite, entire, mostly sessile; stipules sheathing, long-setiferous; flowers mostly 

 solitary or several and sessile in leaf axils, rarely aggregated at summit of 

 branches; calyx teeth 2 to 5, often unequal; corolla funnelform or salverform, 

 the lobes 3 or 4; stamens and style usually exserted, the stamens usually 4 and 

 inserted on the corolla tube, the style filiform and simple or cleft; fruit composed 

 of 2 or 3 crustaceous or leathery indehiscent carpels that usually separate. 



About 50 species, mostly American and African tropics and subtropics. 



1. Fruits leathery, strongly 6-ribbed, glabrous or villous, crowned by 2 prominent 

 calyx teeth, the 2 carpels rarely separated; corolla salverform, the 

 tube 7-10 mm. long 1. D. virginiana. 



1. Fruits crustaceous, not ribbed, commonly hispid or hispidulous, crowned by 

 usually 4 calyx teeth, the carpels readily separated; corolla funnel- 

 form, 4-6 mm. long 2. D. teres. 



1. Diodia virginiana L. Fig. 728. 



Plant diffusely spreading or procumbent from a perennial root, the forking 

 branches to about 6 dm. long, nearly glabrous to villous-hirsute; leaves sessile 

 or essentially so, elliptic-oblong to elliptic-oblanceolate or linear-lanceolate, 

 usually tapering to base, obtuse to acute or acuminate at apex, the margins 

 slightly serrulate, mostly bright-green, to 9 cm. long and 2 cm. wide, usually much 



1552 



