Development of the Vegetation of New York State 61 
ley of the Canisteo shows this sort of thing even more notably. 
At Cameron for example, the high steep north-eastward fac- 
ing valley slope bears an almost pure stand of paper birch. 
Twin flower (Linnaea americana Forbes) was one of the 
ground cover species here. This is a boreal species very 
common in typical Adirondack forest. 
I suppose we may consistently use the name “ cool 
pockets” for situations created by plateau dissection where 
imperfect air drainage permits the gathering of chilled air 
thus favoring unseasonable frosts. 
Possibly the occurrence of such a boreal plant as dwarf 
Canadian primrose (Primula mistassinica Michx.) at differ- 
ent stations in the Alleghany Plateau region might be ex- 
plained in this connection. However, I have not personally 
seen it there. 
Finally, in this connection, the Mohawk Valley shows the 
effect of plateau dissection through slope exposure on dis- 
tribution where apparently temperature differences are cre- 
ated. Thus in the more gorge-like part of the valley from 
Little Falls eastward the south exposures (north side of 
valley) bear the oak, hickory, chestnut type of growth while 
the prominent north exposures of the south rim of the valley 
show a large percentage of paper birch. 
Influence of Lakes upon Zonal Relations in New York 
State. 
This subject has been investigated especially with refer- 
ence to the influence of the Great Lakes upon agriculture 
through their effect upon the occurrence of frosts. Von 
Engeln * in a contribution on the effects of continental glacia- 
tion upon agriculture devotes several paragraphs, (pages 
346-350 of bull. listed below) to a discussion of glacial lakes 
and their effects on local climates and agriculture in which 
he cites especially the work of Whitson and Baker? for 
1Von Engeln, O. D. Effects of continental Glaciation upon Agri- 
culture. Bull. Amer. Geoor. Soc., 46:1914, pp. 241-264 and 336-355. 
2 Whitson, A. R., and Baker, O. E. The climate of Wisconsin and 
its Relation to Agriculture, Univ. of Wis. Agr. Expt. Sta. Bull. 233: 
July, 1912, pp. 25-27, 44, 54, 64. 
