E. V. Wulff —22— Historical Plant Geography 



species forming it, and as to tiie ctianges in species composition of the 

 woody vegetation during the various stages in the post-glacial period. 

 These data constitute exceptionally valuable material for an under- 

 standing of the areas of present-day vegetation and of the changes 

 which these areas have undergone during the Quaternary Period. The 

 investigations now under way of pollen and spores preserved in loess 

 (SuKACHEV, 1937) and more ancient deposits, e.g., in Tertiary, Jurassic, 

 and Carboniferous coals, will, in all probability, disclose much that is 

 new as regards the distribution of genera of present and past floras. 



By the end of the nineteenth century botanical geography, as an 

 independent science, had already attained such development that it 

 seemed possible and necessary to sum up the facts accumulated by it. 

 This found expression in the publication of a number of manuals on 

 phytogeography, in most of which problems of historical plant geog- 

 raphy occupied a place. Among such manuals we may mention the 

 "Handbuch der Pflanzengeographie " by Drude, a renowned investi- 

 gator in the field of botanical geography. In this "Handbuch", which 

 appeared in 1890, we find entire chapters devoted to such problems as 

 areas of distribution and the flora of islands, mountain peaks, and sub- 

 tropical deserts. 



Very interesting and pregnant with ideas is the book of Solms- 

 Laubach (1905), "Die leitenden Gesichtspunkte einer allgemeinen 

 Pflanzengeographie in kurzer Darstellung". In this book the author, 

 among a number of other problems, discusses the manner in which a 

 species penetrates into a new habitat, changes in equilibrium in plant 

 distribution resulting from disturbance in habitat conditions, and 

 insular floras. Lastly, we should not fail to mention Schroter's 

 "Genetische Pflanzengeographie" (ist ed., 1912), which gives a very 

 excellent, though brief, exposition of the principles of historical plant 

 geography. 



Our aim in the present chapter has not been to set forth in detail 

 the entire history of the study of our science, historical plant ge- 

 ography, but only to note the principal stages in this study to serve as 

 an introduction to subsequent chapters. The problems taken up in 

 these chapters are, in most cases, treated in their historical perspective, 

 each chapter constituting a synthesis of numerous works and repre- 

 senting, so to say, a continuation of our historical review. 



Historical plant geography is a science in process of formation. 

 Before it lies a vast field for development, and the more firmly are 

 established its underlying principles and the more data for its up- 

 building are assembled by scierftific investigators, the greater will be 

 its significance as a foundation for other disciplines. 



References: 



Andersson, G., 1897: Die Geschichte der Vegetation Schwedens (Engler's Bot. Jahrb., 

 Vol. 22). 



Beilschmied, C, 1831: Pflanzengeographie nach A. Humboldt's Werke iiber die geo- 

 graphische Verteilung der Gewachse (Breslau). 



BORSZOW, E., i860: Die Aralo-Caspischen Calligoneen (M^m. Acad. Sci. St, Petersb., 

 Sfir. 7, Vol. 3, No. i). 



DE Candolle, Alph., 1855: Geographie Botanique Raisonn^e, Vols. I and 11 (Geneva). 



DE Candolle, Aug. Pyr., 1820: Essai filementaire de Geographie Botanique (in 

 Dictionnaire des Sciences Naturelles", Paris, Vol. 18). 



