294 ANNUAL OF SCIENTIFIC DISCOVERY. 



cases, and all cases where the same plant is supposed to be indig- 

 enous on both sides of the Atlantic no less than 233 distinct 

 species of plants have been imported among us from the Old 

 World, all of which have now run wild here, and many of which 

 are the worst and most pernicious weeds that we have to contend 

 against. In the United States "Agricultural Report" for 1865 

 (pp. 510-519) will be found a list of 99 of the principal "Weeds 

 of American Agriculture," by the late Dr. Win. Darlington. Of 

 this whole number no less than 43, or nearly one-half, are species 

 that have been introduced among us from the Old World. Among 

 these we may enumerate here, as the best known and the most 

 pernicious, butter-cups (two species), shepherd's purse, St. John's 

 wort, cow-cockle, May-weed or dog-fennel, ox-eye daisy, common 

 thistle, Canada thistle, burdock, plantain, mullein, toad-flax, bind- 

 weed, Jamestown (Jimson) weed, lamb's quarter, smart-weed, 

 field garlic, fox-tail, grass, and the notorious cheat or chess. And 

 to these we may add the common purslane, which, through some 

 strange oversight, has been omitted in Dr. Darlington's catalogue. 



It will be supposed, perhaps, since there are about as many 

 voyages made from America to Europe as from Europe to Amer- 

 ica, that we have fully reciprocated to our transatlantic brethren 

 the favors which they have conferred upon us, in the way of nox- 

 ious insects and noxious weeds. It is no such thing. There are 

 but very few American insects that have become naturalized in 

 Europe, and even these do not appear for the most part to do any 

 serious amount of damage there. For example, on one or two 

 occasions single specimens of our army-worm moth (Leucania 

 unipunctd) have been captured in England ; but the insect has 

 never spread and become ruinously common there, as it con- 

 tinually, in particular seasons, does in America. Our destructive 

 pea-bug (Briiclms pisi) has also found its way to Europe ; but al- 

 though it is met with in England, and according to Curtis has be- 

 come naturalized in the warmer departments of France, Kirby 

 and Spence expressly state that it does not occur in England " to 

 any very injurious extent," and Curtis seems to doubt the fact of 

 its being naturalized in England at all. Again, the only species 

 of white ant that exists within the limits of the United States 

 ( Termes frontalis) has been known for a long time to be the guest 

 at the plant-houses of Schbnbrunn, in Germany, but is not re- 

 corded to have ever as yet spread into the surrounding country. 

 As to our American meal-worm (Tenebrio obscurus), Curtis states 

 that it has been introduced into England along with American 

 flour, and that it is sometimes abundant in London and the prov- 

 inces ; but Kirby and Spence say not one word about it, and it 

 seems to be confined to the English sea-ports, and the places 

 where American flour is stored, without spreading into the adja- 

 cent districts. 



A very minute yellow ant, however (Myrmica molcsta) , which 

 is often very troublesome with us in houses, has, according to 

 Frederick Smith, " become generally distributed and naturalized" 

 in houses in England ; and Kirby and Spence state more specifi- 

 cally, that " it has become a great pest in many houses in Brighton, 



