116 THE AMERICAN BOTANIST 



it will not be long before our clovers and the alfalfa will be as 

 badly infested with dodder as they are in Europe. I might 

 say that not only the regular clover dodder of the Old World 

 has come into this country and spread so rapidly, but at least 

 one native species of dodder has sufficiently changed its habitat 

 to become a serious pest upon the clovers. — Charles E. Bessey. 



Weed Immigrants. — Three years ago in making a 

 garden, the writer had occasion to break up a piece of prairie 

 sod that had not been cultivated for twenty years or more. So 

 far as could be seen, and as shown by adjacent pieces of the 

 same sod, weeds were practically absent, but in the piece of 

 ground broken up all the old familiar species at once appeared 

 to dispute possession with the crops. Some of the most per- 

 sistent of these are burdock, clotbur, plantain, dandelion, shep- 

 herds purse, prickly lettuce, sour dock, curled dock, mullein, 

 thistle, purslane, butter-and-eggs, pigweed, white amaranth, 

 spurge, quack grass, pepper grass, rag-weed, horse-weed, flea- 

 bane, mustard and sweet clover. It would be a difficult matter 

 to say where they all came from. Doubtless many were lying 

 in the soil waiting for an opportunity, others probably were 

 from plants that year after year had grown among the grasses 

 without attracting notice, and still others were probably blown 

 onto the soil from other fields. It is quite likely that any piece 

 of grass-land is thus seeded with weed seeds every year but 

 the grass is too well established to permit them to grow. 



