213] FLORA OF COLUMBIA AND VICINITY >Jl 



sists of prostrate, mostly succulent, plants, such as Portulaca 

 olera-cea, P. neglecta, Euphorbia maculata, E. nutans, and Mol- 

 lugo verticillata. 



h. Ruderales setarioides. The foxtail association con- 

 sists of the weedy grasses. Its species occur in all other ruderal 

 societies but often the grasses form a weedy sward consisting 

 of Panicum sanguinale, Paspahim setaceum, Elcusine Indica, 

 and the various species of Setaria and Eragrostis. Gardens and 

 waste grounds support the pigw^eed association the first 

 year, but by the second season these grasses often become 

 established. 



i. Ruderales arctioides. The burdock association oc- 

 cupies waste places, unkept yards, and waysides. It consists 

 of large, coarse plants, such as Arctium minus, Lactuca virosa, 

 L. Scariola, L. Canadensis, L. Ludoviciana, Rumex crispus, R. 

 obtusifolius, Ahutilon Avicennae, Solanuni nigrum, S. Caro- 

 linense, and many minor weeds and escapes. 



j. Ruderales atriplicioides. The orache association 

 is found along streets and roadsides. Such weeds as Atriplex 

 hastatum^ Chenopodium urhicum, C. anthelminticum, C. ambro- 

 sioides, Melilotus officinalis, M. alba, Polygonum spp., Marru- 

 bium vulgare, Leonurus Cardiaca, Lamium amplexicaule , and 

 Sonchus asper, S. oleraceus, and S. a/rvensis, are representative. 

 Many of these seem not to occur in country districts. Some, 

 such as Polygonum littoralc and Chenopodium ambrosioides, 

 prefer coal ashes and are frequent about cinder walks and rail- 

 road tracks. 



k. Ruderales plantaginoides. The plantain associa- 

 tion of low weeds occurs about houses, along paths, and in 

 yards. Such plants as Plantago Rugelii, P. major. Polygonum 



