APPENDIX. B. 315 



APPENDIX B. 



Additional Remarks on the Biota and Climate of the Sand 



Dune Region. 



by alexander g. ruthven. 



Since this report was written the United States Weather Bureau 

 has issued a bulletin (V) "on the length of the crop-growing season, as 

 determined from the average of the latest and earliest dates of kill- 

 ing frost". According to the charts in this paper the influence of the 

 lakes in checking early and late frosts is not as great along the east 

 as along the west coasts, but still appreciable. The average date of 

 the first killing frost in the autumn comes between 5 and 10 days later 

 and the last killing frost in the spring probably about 5 days earlier on 

 the east coast than in the interior, and the former about 5 days earlier 

 and the latter about 10 days later than on the west coast in the same 

 latitude. This is in harmony with the fact that there are apparently 

 only a few southern forms that push farther northward along the east 

 coast than in the interior. 



