^ 



125 



Warming, E., Plantcsamfund. (Irundlraek af den okolojjiske planle- 



gcografi. — Kjobciihavn 1S95. 

 — » — , Oecology of Plants. An introdiiction lo llic stiidy of planl- 



commiinities. — Oxford 1909. 



— >'— und Graebner P., Eug. Warmings Lehrbuch der ökologischen 

 I Pllanzengeographie. — Berlin 1918. 



Vestal, a. g., a, Local di.stribiition of grashoppcrs in relation lo plant 



associations. — Hiol. Hull., 25, 1913. 

 — »— , b, An associalional study of Illinois Sand Prairie. — Ikill. 111. State 



Lab. Nat. Hist., 10, 1913. ' 

 , a, Internal relations of terrestrial associations. — The American 



Naturalist. Vol. XLVIII, New York 1914. 



— > — , b, Prairie vegetation of a mountain-front area in Golorado. — The 



Botanical Gazette, Vol. LVIII, Chicago 1914. 

 — » — , P'"oothills vegetation in the Colorado front range. — Ibid., Vol. 



LXIV, Chicago 1917. 

 — '— , Phj^togeography of the eastern mountain-front in Colorado. I. 



Physical geographj'^ and distribution of vegetation. — Ibid., Vol. LXVIIl, 



Chicago 1919. 



