734 WEED FLORA OF IOWA 



tard family occur in Australia or New Zealand, althougli shep- 

 herd's purse {Gapsella hursa-pastoris) , common mustard {Brassica 

 arvensis), the hedge mustards {Sisymbrium officinale and S. altis- 

 simum) and peppergrass {Lepi<Mwm apetalum) are common in 

 Europe and Asia. 



Of the pulse family the bird's-foot trefoil (Lotm cornicviatus) 

 occurs in Europe, Asia, Africa and Australia; the indigo plant 

 {InMgofera hirsuta) in Africa, Australia, Papua and Asia. The 

 absence of black medick {Medicago lupulina) and hop clover {Tri- 

 folimn agrwriwm,) from Australia is striking. 



Of the geranium family the common European, African and 

 Asiatic species of storksbill {Erodium cicwta/rium) are absent in 

 Australia and New Zealand and the little yellow flowered sorrel 

 {Oxalis comiculata) is the only representative in New Zealand, 

 Australia and Papua. This species also occurs in Europe, Asia, 

 Africa and America. The only malvaeeous weeds in Australia 

 common also to the United States are sida {Sida spinosa) and 

 butter-print {Aiutilon theophrasti) , both of tropical origin. The 

 former occurs in Europe, Asia, Africa, North and South America, 

 Australia and Papua. The pigweed {Am,ar(mthus retroflexvs) of 

 southern North America is common in Europe but has not reached 

 Australia. None of our troublesome weedy species of dock, which 

 are cosmopolitan, occurs in Australia. Of the smartweeds there 

 are two species, the water pepper {Polygonum hydropiper) 

 (Europe, Asia, North and South America) and slender smartweed 

 (P. la/pathifolium) of Europe, Asia, North and South America. 

 Silky cinquefoil {Potentilla anserina), of the rose family, is com- 

 mon in the west and here and there in northern Iowa; it is found 

 in Europe, Asia, Africa, Australia, New Zealand and North 

 America. Feverfew {Agrim^wia striata) is found in Europe, 

 Africa and North America. None of our Oenotheras is cosmo- 

 politan; however the primrose willow {Jussiaea suffruticosa), & 

 sub-tropical plant, is widely distributed in Asia, Africa, America 

 and Papua. Very few of the Umbelliferae are cosmopolitan. 

 Moore and Mueller record water parsnip {Sium latifolium) for 

 New Zealand and Australia. 



The Mexican Ageratum conyzoides of the sunflower family, found 

 in Africa, Asia, Europe, North and South America, is often weedy. 

 The Spanish needle {Bidens bipinnata) is found in Asia, Europe, 

 North and South America. The small number of plants of this 

 family found in Australia and New Zealand is remarkable. None 



