"WEED MIGRATION 



729 



prickly lettuce {Lactuca scariola) and storksbill {Erodmm cicni- 

 tarium). There are also such native weeds as bee-plant {Cleome 

 serrulata), wild liquorice (Glycyrrhiza lepidota), the squirrel-tail 

 grasses {Eordeum jubatum and H. caespitosum) , prickly lettuce 

 {Lactuca pulchella), pine-apple weed {Matricaria suaveolens) and 

 prickly poppy (Argemone plmtyceras) . In the Rocky mountain re- 

 gion, especially Colorado, many of the more recent introductions 

 are from Europe. Among these are the sweet clovers (Melilotus 

 alia and M. officinalis), black mediek {Medicago denticulata) , 

 purslane {Partvlaca oleracea), dodder {Cuscuta arvensis and C. 



Fig. 551A I 



Fig. 551A III Pig. 551A IV 



Fig. 551-A. Seeds scattered with agricultural seeds. I. Barnyard Grass 

 (EcMnochloa crusgalH). II. Medicago denticulata^ common in alfalfa 

 seed. II. Horehound (.MarruMum vulgare), a, weed commonly scattered 

 with alfalfa seed. Common in the Great Basin country. IV. Wild Buck- 

 wheat or Bindweed (.Polygonum convolvulus), commonly scattered with 

 grain seed. 



(All after Hillman.) 



epithymum), foxtail {Setaria viridis), storksbill {Erodmm cicu- 

 tariii/m), Russian thistle {Salsola kali var. tenuifolia) , vegetable 

 oyster {Tragopogon porrifolius) , goat's beard {T. pratensis) and 

 lamb's quarters {Cheno'podium album). A large number of native 

 plants have become weedy, such as marsh elder {Iva xanthifolia) , 



