bis Teas 
1905] OLSSON-SEFFER—PHYTOGEOGRAPHIC NOMENCLATURE 183 
by GRISEBACH (1838) to designate an aggregation of plants char- 
acterized by a dominant species. But, as his examples show, GRISE- 
BACH considered his formations as having a certain physiognomic 
aspect, and when in 1872 he moderated his conception of the term 
formation to an association characterized by a physiognomic type 
instead of by a dominant species, he only more pronouncedly brought 
forward the conception of a physiognomic unit. Leaving aside all 
the various uses of this term by later writers, we have to consider 
whether the original conception of GrIsEBACH of a general plant- 
topographic or physiognomic unit, such as forest, steppe, tundra, or 
prairie, can be retained in the light of modern investigations. If 
that is the case the name stands, if not it falls. I have endeavored 
to show, in a paper now in print, that we need the term formation 
in the sense of GrisEBACH. Did our limits allow, we might call 
attention to many other instances where we could clear up the 
muddy stream of phytogeographical names. One more example will 
suffice to show how this rule would work. The word zone is now used 
as a technical term in phytogeography to designate at least the fol- 
lowing conceptions: the successive belts of vegetation on a mountain 
side, the horizontal climatic zones of the surface of the earth, the 
belts of vegetation surrounding a pool or succeeding each other on 
a shore, the submerged belts especially of marine algae, the layers 
in a fossil-containing deposit; in many local descriptions it is adapted 
for designating any convenient floral area delimited from others; 
and finally in anatomy the term “zone” is applied to any area dis- 
tinguished in structure from its surroundings. That this multiform 
interpretation of the word zone needs adjustment is manifest. In 
the technical language of a science a term should have only one 
meaning. Nothing but confusion will come from the admission 
of enigmatic terms, and the clarifying process is therefore the one 
we expect the nomenclature of phytogeography will shortly be 
exposed to. If in regard to the term zone we follow the principle given 
above, we have to ascertain what author first introduced it as a tech- 
nical word, and in what meaning it was used by him. In 1839 
Bolssrer designated with 'this term the vertical belts of plants in 
Mountains. In a corresponding sense it had been used for a long 
time previously in topography, as also FLAHAULT? mentions. The 
$ Projet de nomenclature phytogéographique. 1890. 
