4 6 
Paul Jaccard. 
These figures confirm what has been said above, and enable us 
to conclude quite generally :— 
(1) . That in alpine grassland rare species are the most numerous 
{numerous not frequent) and common species the least numerous. 
(2) . That the observed decrease in number in passing from the 
rare to the common species takes place according to a mathematical law 
of the same order as that which expresses the different degrees of 
frequency of organic variations. 
It is almost superfluous to remark that though the number of 
rare species exceeds that of the common ones, this is not true of 
the individuals , and that it is the individuals belonging to the common 
species which are most numerous. 
The data necessary to determine the relative proportion of 
individuals according to the degree of frequency of the species to 
which they belong, in other words individual frequency in relation to 
specific frequency, are still lacking. But it can be seen that the curve 
of individual frequency will be contrary in direction to that of 
specific frequency. 
To sum up, if we consider the commonest species of a given 
station as being the best adapted to the ecological conditions of 
that station, as being, so to say, the mean floristic expression, or 
that which realises the greatest number of individuals, we see that 
around this mean type of maximum individual frequency the others 
are distributed in decreasing numbers according to their decreasing 
degree of adaptation. 
The local distribution of species on each limited portion of 
alpine grassland results then not only from the combination— 
essentially variable from point to point—of ecological factors capable 
of favouring or hindering the extension of competing species, but 
also from a factor of mathematical regularity, showing itself by the 
constant relation existing between the different degrees of frequency 
of species and of associated individuals. And, as we shall see, this 
factor of regularity is not the only one. 
IV. 
In determining for the districts of the Dranses, Wildhorn and 
Trient, or tor wider or more restricted areas, the ratio of the number 
of genera to the number of species which enter into the composition 
of their flora, it may be shown that this ratio—which may be called 
the generic coefficient —varies within fairly wide limits. This is cleat* 
from the following table:— 
