PERTINACITY AND PREDOMINANCE OF WEEDS. 239 
But the test of the theory is, whether weeds and emigrating 
herbs in general are more self-fertilizing or less subject to 
eross-fertilization than the majority of related plants, and 
whether many or any of them are actually self-fertilized 
through a succession of generations. It seemed to us that, in 
a limited way, the weeds which Europe has given to North 
America might answer this question. To keep within bounds 
and to have a case with all the data unquestionable, we will 
collate the weeds of European parentage which evince a domi- 
nating character in the United States east of the Mississippi, 
rere for the purpose to the “ Manual of Botany of the 
Nout United States” and Chapman’s “Flora of the 
Southern States.” The latter, however, adds not a single 
weed from Europe of any predominance. We include only 
those which have taken a strong hold and become prominent 
either by their general diffusion over the area or by taking 
marked possession of certain districts. For examples of the 
latter take Hchium vulgare in Virginia, Ranunculus bulbosus 
and Leontodon autumnale in eastern New England, and. Ge- 
nista tinctoria, which covers certain tracts in the eastern part 
of Massachusetts, although nearly unknown elsewhere. We 
must include several species which as weeds came from EKu- 
rope, although they are probably, some of them undoubtedly, 
indigenous to some part of the United States. 
The following are the herbaceous plants naturalized from 
Europe and of an aggressive character in the Atlantic United 
States. Herbs of recent introduction, and those of however 
ancient naturalization which have not either spread widely or 
increased greatly over a considerable district, are omitted. 
The eighteen species in italic type, nearly half of them 
Grasses, are probably indigenous to some portions of North 
America. In some cases the introduced and the indigenous 
plants have come into contact. 
Ranunculus bulbosus. Raphanus Raphanis- Silene inflata. 
Ranunculus acris. trum. Lychnis Githage. 
Nasturtium officinale. Capsella Bursa-pastoris. Stellaria media. 
Sisymbrium officinale. Reseda Luteola. Portulaca oleracea. 
Brassica Sinapistrum. Saponaria officinalis. Malva rotundifolia. 
