m the Di§t7%utmi qf fegetdbk Forms. 
mass,— -by the number of individuals belonging to the same 
species of Pteris or of Polypodium but they do not predominate, 
if we compare with the total sum of the species of phsenoga- 
mous plants the different forms which compose the two groups 
of Ferns and Compositae. As the multiplication of all the spe- 
cies does not follow the same laws, since they do not all produce 
the same number of individuals, the quotient obtained in di- 
viding the total number of phaenogamous plants by the num*^ 
her of species of different families, does not of itself decide the 
aspect, I might almost say kind of monotony of nature in .the 
different regions of the globe. If the traveller is struck with 
the frequent repetition of the same species, ~with the sight of 
those which predominate by their mass, — ^he is not less so with 
the paucity of individuals of some other species useful to man. 
In the countries where the Rubiaceae, the Leguminosas, or the 
Terebinthaeeae, compose the forests, we are surprised to see how 
rare are the trees of certain species of Ginchona, Haematoxylon, 
and the Balsamiferae. 
In turning our attention to species, we may also, without 
having regard to their multiplication, and to the greater or 
smaller number of individuals, compare in each zone, in an ab- 
solute manner, the species which belong to different families. 
This interesting comparison has been made in the great work of 
M. Decandolle, {Regni Vegetahilis Systema Naturae., vol. i. 
p. 128. 896. 489. 464. 510.). M. Kunth has attempted it with 
more than 8800 Compositae already known up to the present 
day, {Nova Genera^ vol. iv. p. 288.) It does not point out 
what family predominates iri the same degree above the other 
indigenous phaenogamous plants, either by the mass of in- 
dividuals, or by. the number of species; but it presents the 
numerical proportions between the species of the same family 
belonging to a different country. The results of this method 
are generally more precise, because they are obtained without 
valuing the total mass of phaenogamous plants, after being 
freed with care from the study of each isolated family. The 
forms which are the mc^t varied, the Ferns, for example, are 
found under the tropics: it is in the mountainous, temperate, 
humid and shady parts of the equatorial regions, that the family 
of Ferns produces the greatest number of species. In the tern- 
