Baron Humboldt on the Laws which are observed 
tween Calabria and Austria. When the vegetation of South 
Carolina, of Pennsylvania, and of New England, shall be de- 
scribed individually, and with the same degree of exactness, we 
shall notice a regular increase and decrease in the numerical pro- 
portions of families from south to north. At present, we only 
know the general mean of these partial proportions. Many 
countries seem richer in plants, because the botanists have in- 
considerately elevated varieties to the rank of species. In an- 
other country, the travellers often neglect the plants which they 
believe to be the same as those of their own country. But when 
we attend to the great divisions, and when the number of spe- 
cies which we compare is very consideraible, oiir researches are 
favoured with happy compensations. It is thus that the new 
Floras, much more complete of America and Lapland, published 
by Messrs Pursh and Wahlenberg, have not sensibly altered 
the numerical proportions which we find on confining ourselves 
to the old Floras of Michaux and Linn^us, (Berl. Jarlih. der 
Pew. b. i. s. 24.). Whatever maybe the corrections which shall 
be made in my work, I am persuaded beforehand, that the more 
that exact observations are accumulated, and the more we look 
beyond the same hemisphere, the same system of agroupmenL the 
partial variations of the coefficients will be found not to be made 
by sudden starts, but according to invariable laws. It may be 
that the tropical proportion of the Malvaceae is or in- 
stead of ^^ 3 ., but it is not the less certain, that the Leguminosae 
and the Malvaceae increase toward the equator, while the Jun- 
ceae and the Ericeae increase toward the pole. One may recall 
in doubt the quantities of the variations, the rapidity of the in- 
crease, but not its direction. 
On comparing the coefficients which belong to the same fa- 
milies, in different zones, we find, in the rapidity of the increase, 
contrasts strongly marked. In the Old Continent, the propor- 
tions of the Gramineae, the Leguminosae, and the Euphorbia- 
ceae, change much less from the temperate zone to the equator, 
than from the temperate zone to the pole. 
Those who are accustomed to consider each phenomenon in 
an absolute and irrelative point of view,-— who regard the mean 
temperature of places, the laws which are observed in the varia- 
iiions of terrestrial magnetism, with the proportions between births 
