THE STRUGGLE FOR EXISTENCE 389 
18. Cow herb,* Saponaria Vaccaria. 
19. Daisy, oxeye,* Chrysanthemum Leucanthemum. 
20. Dandelion,* Taraxacum officinale. 
21. Dock, Rumez crispus. 
22. Dog fennel,* Anthemis cotula. 
23. Fox-tail grass,* Setaria glauca. 
24. Horse-nettle, Solanum carolinense. 
25. Jamestown weed or Jimson weed,* Datura Stramonium 
or D. Tatula. 
26. Johnson grass, Andropogon halepensis. 
27. Mallow,* Malva rotundifolia. 
28. Milkweed, Asclepias Cornutt. 
29. Nettle, Urtica gracilis. 
30. Pigweed,* Amarantus retroflexus. 
31. Pigweed,* Chenopodium album. 
32. Plantain,* Plantago major. 
33. Pokeberry, Phytolacca decandra. 
34. Purslane, Portulaca oleracea. 
35. Quick-grass,* Witchgrass, A gropyrum repens. 
36. Ragweed, Ambrosia artemisicfolia. 
37. Rib grass,* Plantago lanceolata. 
38. Sand bur, Cenchrus tribuloides. 
39. Shepherd’s purse,* Capsella Bursa-pastoris. 
40. Smartweed, Polygonum Hydropiper. 
41. Sorrel,* Rumezx Acetosella. 
42. Spanish needles, Bidens bipinnata. 
43. Sticktights, Desmodium canadense. 
44. Thistle,* Cirsium lanceolatum, C. arvense. 
45. Yarrow, Achillea Millefolium. 
457. Origin of Weeds.!— By far the larger proportion 
of our weeds are not native to this country. Some have 
been brought from South America and from Asia, but 
most of the introduced kinds come from Europe. The 
importation of various kinds of grain and of garden-seeds, 
1 See the article “‘ Pertinacity and Predominance of Weeds,” in Scientific 
Papers of Asa Gray, selected by C. 8. Sargent, Vol. II, pp. 234-242. 
