BIBLIOGRAPHY 141 



made between intermediate and ultimate stages, and it is 

 tlius possible to determine witii considerable accuracy and 

 within a few years the sequence of stages in a succession 

 that requires a century or more for its complete develop- 

 ment. In the Boeky mountains, gravel slides (talus slopes) 

 are remarkably frequent. They occur in all stages of de- 

 velopment, and the alternating slides of different ages fur- 

 nish an almost perfect record of this succession. This 

 method lacks the absolute finality which can be obtained by 

 following a succession in one spot from its inception to final 

 stabilisation, but it is alone feasible for long successions, i. 

 e., those extending over a score or more of years. When it 

 comes to be universally recognized as a plain duty for each 

 investigator to leave an exact and complete record in 

 quadrat maps and quadrat photographs of the stages 

 studied by him, it will be a simple task for the botanists of 

 one generation to finish the investigation of the successions 

 begun by their predecessors. 



BIBLIOGRAPHY 



1749 Biberg, I. J. Oeconomia Naturae. Amoen. 



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 1842 Steenstrup, J. Geognostisk-geologisk-Under- 



sOgelse i det nordlige 



Sjalland 

 1844 Berg, B. v. Das Verdrangen der Laub- 



walder durch die Pichte 



und Kiefer. Grisebach 



Berichte 1844 : 15 



1850 Humboldt, A. v. Views of Nature 125, 213 



1851 Vaupell, 0. De Nordsjaellandske 



Skovmoser 



1852 Henfrey, A. The Vegetation of Europe 67 



1855 De CandoUe, A. G6ographie Botanique Bais- 



onn6e 743 



1856 Hofmann Der nOrdliche Ural und 



Kttstengebirge Pae-Choi 



