CEREAL PESTS WEEDS 453 



494. Wild buckwheat (Polygonum convolvulus, Linn.). 

 This weed is found frequently in grain fields, and the 

 seeds often occur in commercial grain. It is a climbing 

 or twining vine, much branched, rather rough, with naked 

 joints, and 1 to 4 feet in length ; leaves thin, glabrous, ar- 

 row-shaped, and situated on long petioles ; flowers, which 

 arise in small clusters in the axils of the leaves, small, 

 greenish, and produced on short, slender stalks; flowers 

 also occurring on loose terminal racemes. Flowering 

 goes on from June throughout the summer. Seeds are 

 matured in July, and are dull jet black, 3-sided, and ellip- 

 tical to obovoid in shape. The angles of the seeds are 

 rounded and the faces concave (Fig. 141 c). 



The seeds can be removed from seed grain by screening. 

 Rotations, including intertilled crops and a grass crop, 

 will control the weed. Disking immediately after har- 

 vest, to induce germination, and plowing under the result- 

 ing plants later, are recommended. 



495. Buffalo bur or bull nettle (Solanwn rostratum, 

 Dunal). This is one of the worst weeds of the middle 

 and southern Great Plains. The plant is herbaceous, but 

 woody when old, hoary or yellowish, 8 inches to 2 feet 

 high, and covered with stellate pubescence. The branches 

 and main stems are covered with yellow sharp prickles ; 

 leaves melon like, 1 to 3 times pinnatifid, lobes roundish or 

 obtuse and repand, covered with short pubescence, hairs 

 stellate ; flowers yellow, an inch in diameter, nearly regu- 

 lar ; fruit a berry, but inclosed by a close-fitting prickly 

 calyx; seeds thick, irregular, rounded, wrinkled, with 

 numerous small pits, surrounded by a gelatinous sub- 

 stance (Fig. 141 /). Late in the fall the plant loosens 

 from the soil, and is blown about as a tumble weed 

 (492). 



