400 Flahault : Phytogeographic Nomenclature 



the word zone expresses a space which is clearly limited, as for in- 

 stance that portion of a sphere's surface which is contained be- 

 tween two parallel lines (and accordingly this name agrees with the 

 fundamental climatic-botanic zones) as a space is compared to a 

 band. The word is used in this sense in geology, astronomy, 

 meteorology and in military science. With this precise significa- 

 tion it expresses better than all others successive stages of vegeta- 

 tion from the base to the summit of mountains. In this exact 

 sense the word has been adopted by French phytogeographers. 

 " At an elevation of 11,000 feet, said Edmond Boissier, in 1839, 

 one may expect to find vegetation distributed in distinct zones and 

 this is what actually happens, but settling the delimitation of these 

 zones offers many difficulties.* * *" * Dr. Christ has likewise 

 adopted this French interpretation of the word zone when he says 

 that "the differences which occur in the plant world when we 

 ascend from the plain to the snow limit convey to us the principle 

 of zones. It is sufficient to cast a glance even from a distance 

 over one of the chains of our Alps to ascertain that the vegetation 

 which covers it is separated into very distinct zones with well-accen- 

 tuated delimitations, f 



Let us sum up all that has preceded by enumerating only the 

 series of units covering the general surface of the globe, such as 

 we think possible to subordinate one to another : 



1 . GROUP OF REGIONS. 



2. Regions (Marti us, 1831); 



3. DOMAIN. 



4. Sector. 



3. DISTRICT (Bezirk, Engler, 1879). 



6. SUBDISTRICT. 



7. Station (Wimmer, 1 844). 



The word zone would be applied only to those stages of vegeta- 

 tion which are superimposed in altitude, according to the signifi- 

 cation given to it by Boissier in 1839. 



II. Nomenclature of Biological Units 



The nomenclature of biologic units is more simple a priori. 

 It is necessary to recognize, however, that although the disorder 



*E. Boissier, Voyage dan le midi de l'Espagne, 1 : 185. 1839. 



Christ 



1883. 



