45 



seems to indicale llial even under condilions so nearly C([iiall\ 

 favouiable for two competitors Ihat a slij^ht or al leasl very lem- 

 porary disturbance may change the ecfuilibrium in fnvour of Ihe 

 less lit, yet the stronger competilor again (luickly siippl.inls tlic 

 other as soon as the disturbance has ceased. 



Urbain & Marty havc studied recently changes in vegetation 

 caused b}- Talpa mining. 



IJTI-nUTUI^E CITKl): 



I^AKROVV, E. P., On the Ecology of tlie Vegetation of I?recklaiid. II. 



I^^actors relating to the lielative Distributions of (-aliunallcalli in 



Brecliland. — Journal of Hcology 4, 1916. 

 — » — , D:o III. General Eflects of Rabbits on the Vegetation. — Ibid. 



5, 1917. 

 Palmgren, A.. Studier öfvcr löfängsområdena på .Mand I— III. — .\cla 



Soc. pro Fauna et Flora fenn. 42, Nr. 1, Helsingfors 1915 & 1917. 

 HoMELL, L.-G., Sur la rcgle de distribution des frécpienecs. — Svensk 



Bot. Tidskr. Bd. 14, 1920. 

 Urbain, A. -G. & Marty, Pierre, Inlluence du travail souterrain des taupe.s^ 



sur la flore des paturagcs du Cantal. — Comptes rcnd .\cad. Se. 



Paris 171, 1920. 



