GENUS 10. 



BUCKW 1 1 EAT FAMILY. 



I. Tracaulon sagittatum (L.) Small. Arrow-leaved Tear-thumb. Fig. 1648. 



Polygonnin sagittatum L. Sp. PI. 363. i753 

 Tracaulon sagittatum Small, Fl. SE. U. S. 381. 1903. 



Annual, light green, stem slender, weak, decum- 

 bent, or climbing over other plants by the abundant 

 sharp recurved prickles which arm its 4 prominent 

 angles. Leaves lanceolate-sagittate or oblong- 

 sagittate, i'-3' long, obtuse or acute at the apex, 

 slightly rough on the margins, the lower petioled, 

 the upper subsessile ; petioles and lower surface of 

 the midribs prickly; ocreae oblique, not ciliate, 

 fringed at the base by a few bristle-like prickles, 

 flowers in rather dense terminal heads or racemes; 

 calyx greenish or rose-colored; stamens usually 8; 

 style 3-parted to below the middle ; achene 3-angled, 

 oblong-pyramidal, thick-pointed, ii" long, dark red, 

 smooth, shining. 



In wet soil, Newfoundland and Nova Scotia to the 

 Northwest Territory, south to Florida and Kansas. As- 

 cends to 3000 ft. in Virginia. July-Sept. 



2. Tracaulon arifolium (L.) Raf. Halberd- 

 leaved Tear-thumb. Fig. 1649. 



Polygonum arifolium L. Sp. PI. 364. 1753. 

 Tracaulon arifolium Raf. Fl. Tell. 3: 13. 1836. 



Perennial, stem ridged, reclining, 2-6 long, the 

 ridges armed with recurved prickles. Peduncles 

 and pedicels glandular or pubescent ; leaves broadly 

 hastate, long-petioled, i'-io' long, pubescent or 

 glabrous beneath, the apex and basal lobes acumi- 

 nate ; petioles and stronger nerves prickly ; ocreae 

 oblique, fringed at the summit with short bristles 

 and at the base with slender prickles ; flowers in 

 terminal and axillary heads or racemes ; calyx rose- 

 color or greenish, 4-parted; stamens 6; style 2- 

 parted ; achene lenticular, broadly obovate, 2" long, 

 strongly biconvex, dark brown, smooth, shining. 



In moist or wet soil, New Brunswick and Ontario to 

 Minnesota, south to Georgia. Sickle-grass. Scratch- 

 grass. July-Sept. 



ii. TINIARIA Webb & Moq. ; Webb & Berth. Hist. Nat. Canar. 3 : 221. 1836-40. 



Annual or perennial often scurfy unarmed twining vines. Leaves alternate, mem- 

 branous or leathery, cordate or hastate. Ocreae oblique, naked or fringed at the top or the 

 base. Racemes loosely flowered, axillary or terminal, often paniculate, leafy-bracted or 

 naked. Sepals 5, green, white or yellowish, 2 exterior, 2 interior and i with one edge 

 interior and one edge exterior, this sepal and the two outer keeled or strongly and con- 

 spicuously winged. Pedicels slender, reflexed and articulated. Stamens 8, included ; fila- 

 ments short, converging. Styles 3, short or almost wanting, distinct or rarely united. 

 Achenes 3-angled, dark brown or black, included, smooth and shining or granular and dull. 

 Endosperm horny. Cotyledons accumbent. [Latin, worm, referring to the habit of the 

 plants.] 



About 8 species, natives of North America and Asia. Type species : Tiniaria Convolvulus (L.) 

 Webb. & Moq. 



Outer segments of the calyx unchanged, or keeled in fruit. 



Achene granular and dull ; ocreae not bristly. i. T. Convolvulus. 



Achene smooth and shining : ocreae bristly. 2. T. cilinodis. 



Outer segments of the calyx conspicuously winged in fruit. 

 Calyx-wings not incised. 



Fruiting calyx s"-6" long, the wings crisped. 3. T.scandcns. 



Fruiting calyx $"-4" long, the wings rather flat. 4. T. dnmctonun. 



Calyx-wings incised. 5. T. cristata. 



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