Nov. 1905, | ACACIAS IN VARIOUS PLACES. 123 
ACACIAS IN Various PLaces: A Stupy IN ASSOCIATIONS. 
By G. F. Scort Extiot, M.A., B.Sce., F.L.S. 
In the study of Plant Associations, one is met at the 
outset by serious difficulties arising from the various classifi- 
cations adopted by different authors. 
Those employed in England and in France are, so far as 
the general idea is concerned, very much the same: but in 
Germany, in the United States, in Russia, and in Scandinavia 
respectively, the system of classification does not agree, even 
in essentials, either with that used in France or with each 
other, whilst as regards details almost every observer seems 
to make up his own descriptive terms. 
Thus this, the youngest department in botany, runs a risk 
of being choked, whilst still growing up,in a thorny wilder- 
ness of terminology, which nevertheless shows. how rich and 
fertile is the field of inquiry. 
The reason of this confusion seems to be that botanists 
have at once rushed to the task of mapping out associations 
and giving them names. But no one would make a geological 
map without having both a definite idea of the succession of 
geological strata and of the numerous variations in the 
structure of ordinary sedimentary strata by the occurrence 
of volcanic dykes. I think there is just as definite and 
regular a succession of associations on any one spot as there 
is of geologic strata, whilst wherever rock, water, or desert 
conditions interrupt the ordinary climatic factors, whole 
series of transitional or fringing associations occur which 
connect the normal type of the district with rock, water, 
or desert associations. It is a mistake in policy, in my 
opinion, and produces confusion, if these transitional fringes 
are classed as associations in themselves. To attack the 
general question is much too dangerous an attempt for a 
short paper, and I shall only try to show how, if we recog- 
nise that many associations bordering desert countries are 
only transitional, the study of the subject is very much 
simplified. 
The characteristic plant of all those associations which 
surround deserts in sub-tropical and tropical countries is the 
genus acacia. It is a very variable genus, and contains some 
