Flahault : Phytogeographic Nomenclature 403 



biologic and physiologic knowledge, the term biologic forms 

 (Lebensform, Vegetationsforni) which was previously but vaguely 

 understood. 



Grisebach understood by it forms of the same character which 

 may or may not have morphologic affinities. It is known now 

 that environment influences structure ; this conception has been 

 given precision. For example, when we speak of the ericaceous 

 form we do not intend to treat only of the physiognomy, but also of 

 a number of details of structure of which the outward appearance 

 is but the collective expression. 



Grisebach, in giving a vague 



A 



not think of defining more clearly biologic groups which had 

 as a basis the vague definition of biologic form such as he 

 had conceived it. In 1838 he endeavored to group them under 

 the name of Phytogeographic formation {Pflanzengeographische 

 Formation, Vegetationsformatiori). " Natural formation includes 

 plants which may be very different, but which have properties 

 and characters in common, which may be summed up by pointing 

 out several species which exemplify the special characteristics of 

 the whole.' ' So understood, forest, prairie and steppe are natural 

 formations. But taking up this definition again to introduce more 

 and more specious distinctions, Grisebach in 1872 distinguished 

 fifty-four formations. Prof. Drude enumerated twenty-seven in 

 the hercynien group.* In 1896 he distributed the different forest 

 types of Germany into fourteen formations.! Kurz saw eight 

 formations in the forest of Burma. J Hult divides the vegetation 

 of northern Finland into half a hundred formations. § The primi- 

 tive idea has disappeared ; thanks to the new interpretation, the 

 ensemble disappears under the details, the tree hides the forest. 



This diversity of interpretation has caused great difficulty in ex- 

 pressing facts relative to botanic geography. 



Our forests, whether they be composed principally of oaks or 

 of beech, or oaks and beech trees mixed, or associated with horn- 

 beams or maples, etc., correspond none the less to a uniform type. 



* Drude, Ueber die Principien . . . 1889. 

 t Drude, Deutschlands Pflanzengeographie, 1896. 

 t Kurz, Forestflora of British Burma, 1877. 

 Hult, Forsok till analyt. Behandling, 1 881. 



