Chapter XI —205— Concept of Floral Elements 



Within the Hmits of a natural floral region (or country comprised 

 within such a region) there may be found territories in which specific 

 ecological conditions predominate, e.g., mountain systems, river valleys, 

 etc., thanks to which in these territories there have found refuge whole 

 colonies of alien plants, called by Eig inclusions ("encluses"). The 

 latter may either form independent associations or may join associ- 

 ations formed by the basic elements. In such cases it is necessary to 

 speak either of alien inclusions in the flora or of inclusions in the com- 

 position of the basic elements. These inclusions, for the most part, do 

 not have any direct connection with the regions in which they origi- 

 nated. Historically, they constitute remnants of ancient migrations of 

 mother elements ("elements meres"), which gave rise to them. 



While in the foregoing case we have to do with elements alien to the 

 given flora and restricted to definite territories, in other cases a floral 

 region may contain a relatively small number of species belonging to 

 alien floras that have penetrated within its limits but are not confined 

 to any narrowly restricted ecological conditions and consequently not 

 occupying any definite territory. Such species Eig terms penetrants 

 ("penetrations"). The occurrence of such penetrants in the compo- 

 sition of any given flora is due, for the most part, to the existence of 

 favorable ecological conditions (e.g., the penetration of a certain number 

 of Mediterranean elements into western Europe without occupying any 

 definite territory there). In many cases these penetrants are likewise 

 remnants from the migrations of ancient elements during periods favor- 

 able for such migrations. 



Every floral region possesses in its flora, besides its own basic ele- 

 ments and besides inclusions and penetrants, if such there be, a large 

 nimiber of other species more or less widely distributed not only within 

 the limits of this region but in adjoining regions. These species Eig 

 ca.\ls plant links ("plantes de liaison", "Verbindungs-Sippen"). These 

 adjoining regions have been in juxtaposition since ancient geological 

 times, and they are closely linked by common climatic conditions and 

 other ecological factors. Hence, these plant links are indicators not 

 only of floristic but also of ecological and phytocoenological bonds. 

 It is natural that neither wides ("polychores" in Eig's terminology) 

 nor weeds can be classed as plant links. In some cases it may be found 

 possible to establish the existence of entire groups of plant links 

 (" grouppements de liaison"). 



Hence, from Eig's point of view, among the autochthonous species 

 of a natural flora we find not only elements of this flora but also plant 

 links and wide-ranging polychores. While we agree that not every 

 autochthonous species entering into the composition of a given flora 

 can be included among its elements, we believe, as already noted, that 

 wides ("polychores") may be so included, provided their centers of 

 origin and time of dispersal have been determined. 



Returning now to the concept "element", we wish to consider the 

 question as to which of the above-enumerated types of elements is of 

 most importance or, in other words, on which of them we should chiefly 

 base an analysis of a flora. Some investigators consider genetic ele- 

 ments of most importance; others, such as Walter (1927), maintain 

 that geographical elements constitute the only reliable basis for sub- 

 dividing a flora into its constituent parts. 



