of vegetable Forms. 449 
The number of vegetable species described by botanists, or ex- 
isting in European herbals, extends to 44000, of which 6000 
are agamous. In this number we had already included 3000 
new phanerogamous species enumerated by M. Bonpland and 
myself. France, according to M. Decandolle, possesses 3645 
phanerogamous plants, of which 460 are glumacee, 490 com- 
posite, and 230 leguminous, &c. In Lapland there are only 
497 phanerogamous plants; among which are 124 glumacee, 
58 composite, 14 leguminous, 23 amentaceous, &c. See my 
Essay on the Geography of Plants published in 1806, and of 
which [ am preparing a new edition. 
In order to account for the differences which exist sometimes. 
between the relations exhibited by Germany, North America, 
and France, we must take into consideration the more or Jess 
temperate climates of those regions. France extends from 42}° 
to 51° of latitude. On this extent the mean annual heat is 16° 7” 
to li’: the mean heats of the summer months are 24° to 19°, 
Germany, comprised between 46° and 54° of latitude, pre- 
sents at its extremities mean annual temperatures of 12° 5’ and 
8° 5’. The mean heats of the summer months there are 21° 
and 18°. North America, in its immense extent, presents the 
most varied climates. Mr. Pursch has made us acquainted with 
2000 phancrogamous plants which grow between the parallels 
of 35° and 44°; consequently under mean annual temperatures 
of 16° and 7°. The Flora of North America is a mixture of 
several Floras. The southern regions give it an abundance of 
malvacee and composite plants; the northern regions, colder than 
Europe under the same parallel, furnish to this Flora abundance 
of rhododendrons, amentacez, and conifere. The caryophyllee, 
the umbelliferse, and the erncifere are in general more rare in 
North America than in the temperate zone of the old conti- 
nent*, 
These constant relations observed on the surface of the globe, 
in the plains from the equator to the pole, are again traced in 
the midst of perpetual snows on the summits of mountains. We 
may admit, in general, that on the cordilleras of the torrid zone 
the boreal forms become more frequent. It is thus that we see 
prevail at Quito on the summit of the Andes, the ericinex, the 
* For the sake of those who are not much conversant in descriptive bo- 
tany, we shall here enumerate the plants which serve as a type to the forms 
or principal families: Glumacee, rushes, tares; orchidea, orchis, satyrion, 
vanilla; labiate, save ; ericinez, broom; composit@, coltsfoot, tussilago; ru- 
biacea, madder, quinquina; wnbellifere, fennel; crucifere, radish, cab- 
bage; malvucee, cotton; leguminose, furze, truffles, sensitive plant; 
euphorbiacea, milky thistle; amentacea, willow, oak; conifere, pine, yew, 
juniper. 
Vol, 47. No. 218. June 1816, Ff rhodo- 
