696 WEED FLORA OF IOWA 



alien immigrants he gives as follows: Mediterranean region, 33 

 species ; tropical America and warm temperate regions, 13 ; tropical 

 Africa, 16; Australia, 1; temperate North America, 1; temperate 

 South America, 1; uncertain origin, 16. It is interesting to note 

 that the following Iowa species are abundant and troublesome in 

 the Transvaal (the exceptions being capitalized) : mayweed 

 (Anthemis cohda), black mustard (Brassica nigra), hemp (Can- 

 nabis sativa), shepherd's purse (Capsella bursa-pastoris), goose- 

 foot (Chenopodium album), wormseed (Chenopodium ambro- 

 sioides), nut grass (Cy perns escidentus), jimson weed (Datura 

 stramonium), wire grass (Eleusine Indica), fleabane (Erigeron 

 canadensis), shoo-fly (Hibiscus trionum), common morning-glory 

 (Ipohoea purpurea) , toad flax (Linaria vulgaris) , darnel (Lolmm 

 temidentum) , lady's sorrel (Oxalis cornicidata) , ribgrass (Plantago 

 lanceolata), common plantain (Plantago major), black bindweed 

 (Polygonum convolvulus) , larger knotweed (Polygonum erectum) , 

 purslane (Portulaca oleracea), jointed charlock (Raplianus raplia- 

 nistrum), sheep sorrel (Rumex acetosella), yellow dock (Rumex 

 crispus), smooth tobacco (Nicotiana glauca), cow-herb (Saponaria 

 vaccaria), bristly foxtail (Setaria verticillata) , black nightshade 

 (Solanum nigrum), dandelion (Taraxacum officinale), chickweed 

 (Stellaria media), sow thistle (Sonchus oleraceus), goat's beard 

 (Tragopogon porrifolius) , vetch (Vicia sativa). In addition to 

 the above plants, Davy lists quite a number which are common in 

 the states to the south of Iowa and in California. Such plants as 

 castor-oil bean (Ricinus communis), zinnia (Zinnia pauciflorus) , 

 marigold (Tagefes erecta), cosmos (Cosmos bipinnatus), cockscomb 

 (Celosia cristata), four-o'clock (Mirabilis jalapa), evening primrose 

 (Oenothera grandiflora) , Xylopleurum tetrapterum, Mexican poppy 

 (Argemone mexicana) are commonly cultivated in Iowa. Some, like 

 Argemone, Oenothera and Cosmos, occasionally escape in Iowa. In 

 a classification of these weeds, Davy places the alien plants under 

 the following heads : I. Colonists (species not yet showing signs 

 of spreading) ; shepherd's purse (Capsella bursa-pastoris), cat's-ear 

 (Hypochaeris radicata), (one of the most common weeds on the 

 Pacific coast and spreading in New England, not reported from 

 Iowa), black bindweed (Polygonum convolvulus) (common every- 

 where in Iowa), toad-flax (Linaria vidgaris) (common in the 

 north). II. Adventive (occasional, but spreading); mayweed 

 (Anthemis cotula), Mexican poppy (Argemone mexicana), Cosmos 

 bipinnatus, morning-glory (Ipomoea purpurea), darnel (Lolium 



