164 HEREDITY AND EVOLUTION IN PLANTS 



rare cultivated vine, but since that time, according to 

 Miss Andrews, 1 ''it has spread over practically the whole of 

 the Eastern States, from the Gulf of Mexico to the estuary 

 of the Hudson, making itself equally at home in the low 

 hammocks of the Coastal Plain, on the old red hills of the 

 Piedmont region, on the stony ramparts of the Lookout 

 Plateau, and onward for a thousand miles up the great 

 Appalachian Valley." The adaptability of the plant, as 

 indicated by this description of its habitats, in no doubt a 

 large factor in its rapid spread, for while it is a profuse 

 bloomer under cultivation, it tends to become weedy, as 

 it grows wild, blossoming rarely and therefore setting few 

 seeds. But its wide distribution must have been accom- 

 plished by the dissemination of its seeds, and in this Miss 

 Andrews believes that the most probable agents are birds, 

 to whose feet the small, inconspicuous nutlets, "embedded 

 in a mucilaginous pulp," readily adhere. 



Several species (e.g., the fleabane, Pluchea fcetida) 

 are found in shallow fresh water or fresh or salt water 

 marshes from southern New Jersey to Florida, and then 

 across 120 miles of salt water in Cuba. In this case it 

 seems clearly evident that the seeds have been able to 

 undergo transportation across the Florida strait within 

 comparatively recent times. Examples might be multi- 

 plied, and in such cases discontinuous distribution has 

 little evolutionary significance for the particular species 

 concerned, though the facts may serve to throw light upon 

 other cases that are significant. 



120. Endemism. On the basis of the evolution theory 

 every species originated in some one area (its center of dis- 



1 Andrews, E. F. The Japanese honeysuckle in the Eastern United 

 States. Torreya, 19 : 37-43. Mch. 1919. 



