Flahault : Phytogeographic Nomenclature 401 



is great in the classing of geographic and topographic units, 

 in biologic units it is extreme. To avoid being misled in this 

 labyrinth it would be well to retrace our steps in the course that 

 we have just followed and consider first the elementary units, 

 those which populate stations. It is very encouraging that good 

 works Tvhich have been published during the last few years have 

 commenced to introduce order into the subject by making Asso- 

 ciations the foundation of critical study of botanic geography. 



I did not pretend to make an innovation when I insisted, in 

 1 894, on the necessity of taking the associations of plants living 

 in common in the same station as a starting point for phytogeo- 

 graphic comparisons. It is due to Humboldt that attention was 

 first called to the importance of Plant Associations. In his Essay on 

 the Geography of Plants * in 1807 he showed that the different as- 

 sociations of plants which succeed one another from the base to 

 the summit of Chimborazo depend strictly on temperature, hu- 

 midity, atmospheric pressure, etc. 



In 1820, A. P. de Candolle f urged the necessity of noting 

 all details relating to associations : the station and its local varia- 

 tions, the degree of frequency or rarity of plants, etc., and their 

 grouping into societies. 



This conception therefore has its history. It is necessary that 

 the significance of the term should be precisely stated. Vegetable 

 association is the final expression of vital competition and of adap- 

 tation to environment in the grouping of species. Plants which 

 inhabit the same station are not only connected one with another 

 by simple relations of coexistence, but also by a bond of reciprocal 

 interest, for certain of them receive benefit and profit from the con- 

 ditions caused by the presence of others. The term vegetable 

 association does not imply the harmonious cooperation of diverse 

 tendencies toward a common end of collective advantage, as in all 

 society founded on the principle of division of labor. It applies to 

 the bringing together of specific and morphologic forms which 

 are foreign to one another, for the exclusive profit of each indi- 

 vidual ; they live side by side, following the conformity or diversity 

 of circumstances that suit them, either in the actual conditions of 



Al. de Humboldt, loc. cit., 1807, p. 14. 



Leman 



