about 2 mm. long, 5-parted to below the middle with the lobes broadly oblong, 

 rounded at apex, white with some medial reddish or greenish markings and at 

 anthesis spreading; achene 2-2.5 mm. long, ovoid in over all outline, in transec- 

 tion almost equilaterally triangular (one side, the one not furnished with an 

 inner sepal, usually slightly smaller and more concave than the others), dark- 

 brown at maturity, rather lustrous. 



Infrequent in seasonally moist places on Edwards Plateau and s. part of Plains 

 Country (Andrews, Crockett, Howard, Sutton and Val Verde cos.), Tex., summer- 

 fall; endemic. 



6. Polygonum argyrocoleon Kunze. Persian wiregrass. Fig. 405. 



Taprooted glabrous annual, the roots becoming ligneous toward fall and simu- 

 lating the perennial habit; stems striate, erect with several ascending branches, 

 the whole plant 2-5 dm. tall; upper parts of ocreae hyaline and long-lacerate; 

 petioles adnate to and as long as ocreae; blades jointed to petioles, green, mem- 

 branous, at midstem lance-linear, 1-3 cm. long, narrowed to both ends; upper 

 leaves reduced to minute bracts and the upper internodes shortened so that the 

 flowers are crowded in terminal spikelike clusters 2-5 cm. long or more; calyx 

 about 1.5 mm. long at anthesis, about 2 mm. long in fruit, divided nearly to base; 

 achenes trigonous, reddish-brown, with one face broader than the others, about 

 2 mm. long, very lustrous. 



Infrequent or rare in seasonally moist places such as temporary pools and playa 

 lakes, and in marshy ground, in w. Tex. (Brewster, Hudspeth, Pecos and Upton 

 COS.), N. M. (Lea Co.) and Ariz. (Mohave, Maricopa, Pinal and Yuma cos.), 

 Apr.-Oct.; nat. of Near and Middle East, now adv. in Calif., Ariz., N. M. and 

 Tex. 



7. Polygonum confertiflonim Nutt. 



Glabrous, simple to ascending-branched annual (4-) 6-20 cm. tall, the stems 

 slightly angled; leaves linear, 1-3 (-4) cm. long, 1-2 mm. broad, jointed at base; 

 stipules lacerate, 3-7 mm. long; flowers 2 to 4 per node, subsessile, mostly 

 crowded at the ends of the branches or occasionally a few in the axils of the 

 proximal floral leaves, the lower bracts similar to the leaves, the upper ones 

 shortened and often not exceeding the flowers but usually broadened and more 

 or less white-margined; perianth 1.5-2.5 (usually about 2) mm. long, connate 

 scarcely one third the length, the segments with a greenish midstripe and white to 

 pinkish borders, slightly cucullate-keeled, the 3 outer ones subequal to or con- 

 siderably longer and broader than the 2 inner ones; stamens usually 8, the 3 inner 

 ones anther-bearing, the filaments much-expanded at base, the 5 outer ones with 

 abortive (or no) anthers, the filaments linear; styles 3, connate to midlength, 

 barely 0.3 mm. long; achene 1.5-2 mm. long, yellow-brown to (commonly) 

 brownish-black, usually dull and prominently striate lengthwise but sometimes 

 (even on the same plant) smooth and shining, triquetrous. P. Watsonii Small. 



Meadows, seepage about lakes and vernal pools to dry open ground, in N. M. 

 (Rio Arriba and San Juan cos.) and Ariz. (Coconino Co.), May-Sept.; Mont, to 

 Wash., s. to Colo., N.M., Ariz, and Calif. 



8. Polygonum Kelloggii Greene. 



Simple or sparingly branched glabrous annual, the stem angled, mostly 2-7 cm. 

 tall; leaves few, linear, 5-25 mm. long, mostly about 1 mm. broad, basally jointed; 

 stipules lacerate, 2-7 mm. long; flowers subessile (pedicels to 1 mm. long) in 

 crowded terminal clusters of 1 to 4 and usually also axillary to most of the lower 

 foliage leaves, the stems sometimes floriferous almost to the base; floral bracts 

 linear, nearly divergent, only moderately reduced upward, the upper ones usually 



814 



