Chapter XI — 213 — Concept of Floral Elements 



well express the Tertiary character of the flora which occupied at that 

 time our present-day temperate zone of Europe. In this term the 

 emphasis is placed not on the subtropical nature of those species that 

 we refer to this element but on the present climatic (northern) charac- 

 ter of the region inhabited by this flora that subsequently migrated to 

 the south. 



But of an even more fundamental character is the following con- 

 sideration. Engler and subsequent investigators presumed that the 

 three floras mentioned succeeded one another completely; they en- 

 tirely ignored the existence of different floras at different altitudes, with 

 also a gradual dying out of tropical and subtropical elements and their 

 replacement by temperate and alpine elements, in aU zones of Tertiary 

 Europe, for which there are ample paleobotanic proofs. Nevertheless, 

 there is no doubt that successions of floras have taken place not only 

 as a result of shiftings of the various elements from south to north but 

 also as a result of a shifting of vegetation belts toward the lower alti- 

 tudes and the distribution of these temperate and alpine elements in 

 the plains and their migration from east to west or from west to east 

 within the hmits of the same climatic zone. 



Lastly, it should be noted that the shifting of the tropical and 

 subtropical elements of Eurasia was initiated not from the north but 

 from the east, from eastern Asia, a view to which Engler himself in- 

 cHned in his latest works. From such a viewpoint the term "arctic- 

 Tertiary element" loses its original meaning. In view of their lack of 

 clarity, it would seem advisable to discard both terms — arctic-Tertiary 

 and boreal-Tertiary. 



Although it has not been possible to review here all the extensive 

 literature on floral elements, we believe that the principles we have 

 outlined in this and preceding chapters suffice to indicate the general 

 course to be followed in making analyses of floras. This method of 

 analyzing floras is widely used by plant geographers throughout the 

 world. By summarizing the results of their work one may retrace the 

 main stages in the history of the floras of our globe. 



References: 



Akeschoug, F. W., 1867: Bidrag till den Skandinaviska Vegetations Historia (Lunds 

 Univ. Arsskr.). 



Braun-Bi.anqdet, J., 1919: Essai sur les notions "d'elfiments" et de territoire phyto- 

 g^ographique (Arch. Sci. Phys. et Nat., Vol. s). 



Braun-Blanquet, J., 1923: L'origine et le d^veloppement des flores dans le massif 

 central de France (Pari^. 



Chkist, H., 1867: Ijber die Verbreitung der Pflanzen der alpinen Region der europai- 

 schen Alpenkette (Denkschr. Schweiz. Nat. Ges., Vol. 22). 



Degelius, G., 1935: Das ozeanische Element der Strauch- und Laubflechten-Flora von 

 Skandinavien (Acta Phytogr. Suec, Vol. 7). 



DiELS, L., 1910: Genetische Elemente in der Flora der Alpen (Engl. Bot. Jahrb., 



Vol. 44). 



Drude, O., 1890: Handbuch der Pflanzengeographie (Stuttgart). 



EiG, A., 1931 : Les elements et les groupes phytog^ographiques au.xiliaires dans la 

 flore palestinienne, I. Texte; II. Tableaux analitiques (Fedde's Repert. Spec. Nov., Bei- 

 hefte, Vol. 63). 



Engler, A., 1879, 1882: Versuch einer Entwicklungsgeschichte der Pflanzenwelt, ins- 

 besondere der Florengebiete seit der Tertiarperiode, Vols. I and II (Leipzig). _ 



Gams, H., 1930: Schisma Sendlneri, BreiUelia arcuata und das Rhacomitrietum lanu- 

 ginosi als ozeanische Elemente in den Nordalpen (Revue Bryologique, N. S. Vol. 3, No. 

 1-2). 



