656 PROCEEDINGS OF THE ACADEMY OF [Oct., 



RACIAL VARIATION IN PLANTS AND ANIMALS, WITH SPECIAL REFERENCE 

 TO THE VIOLETS OF PHILADELPHIA AND VICINITY. 



BY WITMER STONE. 



Having for a number of years been interested in racial variation 

 among terrestrial vertebrates and its relation to environment and 

 climatic conditions, I was recently led to make some investigations 

 along the same lines among our phaenerogamic plants, in some genera 

 of which, notably Cratccgus, Panicum, Viola, etc., species and subspecies 

 have of late years been described at a rate quite etjual to that which 

 has prevailed for some time past among the birds and mammals. 



The genus Viola was selected for study because I have long been 

 familiar with the more common species found in the vicinity of Phila- 

 delphia, and because an abundance of material is easily accessible in 

 this neighborhood. 



While my studies have thrown little light upon the relation of 

 variations to conditions of environment, they have enabled me to pre- 

 sent a pretty complete account of the variations exhibited by our 

 local violets which may prove of assistance to those who investigate 

 this interesting genus. 



Any one at all in touch with the progress of systematic zoology 

 and botany must be aware of the enormous number of new species 

 and subspecies that have been named and described during the last 

 decade. By some, especially those who have not gone very deeply 

 into systematic work, this tendency has been severely criticised as 

 unwarranted multiplication of names in the interest of the describer, 

 which tends to render specific identification more difficult on the part 

 of the general student. To those who have given the matter serious 

 consideration, however, it must be evident that slowly but surely 

 our conception of a species has been changing, and that the recognition 

 of a very large number of new forms in systematic work is an obvious 

 necessity on evolutionary and philogenetic grounds. 



The enormous collections that have been gathered together in recent 

 years, especially in the United States, covering thoroughly, as they 

 do, large contiguous areas instead of isolated spots as heretofore, show 

 us that instead of sharply defined widespread species wc have, in 



