3 « 
Paul Jaccard. 
Is the same true of the common species which form the basis 
of the vegetation of the Alps ? 
In order to reply to this question I have considered, in an 
alpine district of fair size, various natural sub-divisions, pre¬ 
senting, besides numerous resemblances in their ecological con¬ 
ditions ( i.e . conditions dependent on soil and climate), a few 
characteristic differences; and I have sought to determine, by 
comparison, the influence of these resemblances and differences 
on the composition of the flora. 
1 . 
My researches have been chiefly carried out on three districts 
about fifty kilometres distant from one another. These are :— 
(1) The upper basin of the Sallanche and of the Trient, (2) the 
massif of the Wildhorn, (3) the upper basin of the Dranses. 
From the topographical point of view these three districts 
present great analogies: all three contain high summits covered 
with snow and ice : all three, except the northern slope of the 
Wildhorn, open to the valley of the Rhone: finally, owing to their 
proximity, the meteorological conditions appear very similar. 
From the petrological standpoint, on the other hand, they are 
sharply dissimilar. The massif of the Wildhorn is essentially 
calcareous; the basin of the Trient includes both gneiss and lime¬ 
stone ; while the basin of the Dranses presents the most various 
substrata, including the Casana schists, carboniferous schists, 
Antigorio gneiss, primitive rocks of the Mont Blanc series, 
calciferous triassic schists, etc. 
Each of the three separate districts is sub-divided into parallel 
valleys, forming as many comparable sub-districts. 
In making a complete list of all the species of plants met with 
in the alpine and niveal zones of each of these three districts, the 
following approximate numbers were obtained:— 
1 . 
Wildhorn (W) 
350 
species. 
2. 
Trient (T) 
470 
3. 
Dranses (D) 
600 
>> 
4. 
The three together - 
660 
Of the 600 species of the basin of the Dranses, about 60 
have not yet been met with in the other two districts: again of the 
470 species of the Trient basin, about 60 are absent from D and 
W : finally about 30 species noted in W are absent from T and D. 
In each case at least half the species noted in one of the 
