xvi ILLUSTRATIONS 



FIGURE PAGE 



242. Quack grass 508 



243. Witch grass 509 



244. Crab grass 510 



245. Wild mustard 512 



246. Kagweed 513 



247. Buckhorn plantain 514 



248. Sheep sorrel 515 



249. Burdock 519 



250. Blue vervain 520 



251. Curled dock 521 



252. Shepherd's purse 522 



253. Lambs' quarters 524 



254. Russian thistle 526 



255. Mallow 528 



256. Prickly lettuce 529 



257. White cockle 530 



258. Purslane 531 



