m. the J)isirihut\on Vegetable Forms. .^79' 
than jth of the entire inags of phsenpgamous plants, (Deean- 
dolle, in ,the Mem. de Jrcueil^ vol. hi. p. 29o.). 
It will be useful to consider at a future period the vegetation 
of the tropics and that of the temperate region between the pa- 
rallels of 40° and 50% according to two different methods, either 
in searching the numerical proportions in the whole of the plains 
and the mountains, which nature presents over a great extent of 
country, or in determining these proportions in the plains alone 
of the temperate zone and of the torrid zone. As our herbaries 
are the only ones that . point out, according to barometrical 
measurement, in more than 4000 plants of the equinoctial re- 
gion, the height of each station above the level of the sea, the 
numerical proportions of the table which I have already pub- 
lished may be rectified, when our work, the Nova Genera^ 
shall be finished, by taking away from the 4000 phsencgamous 
plants which M. Kunth has employed in this work (Prolegom^ 
p. 16.), the plants which grow at above 1000 toises, and by di- 
viding the total number of plants which are not alpine, of each 
family, by that of plants which live in the cold and temperate 
regions of equinoctial America. This mode of proceeding 
should affect more, as we shall show by and bye, the families 
which abound in alpine species, for example, the Gramineae and 
the Compositae. At 1000 toises of elevation, the mean tempe- 
rature of the air is still, on the back of the equatorial Andes, 
centigr., which is equal to that of the month of July at Pa- 
ris. Although on the platform of the Cordilleras, we find the 
same annual temperature as in the high latitudes, (because the 
isothermal line of 8% for example, is the track marked in the 
plains by the intersection of the isothermal surface of with 
the surface of the earth's spheroid,) it is not too much to gene- 
ralise these analogies of the temperate climates of the equatorial 
mountains, with the low regions of the circUmpolar zone. These 
analogies are not so great as might be thought ; they are modi- 
fied by the influence of the partial distribution of the heat in 
the different parts of the year. (Proleg. p. 54,, and my Jfe- 
moire sur les Lignes Isothermes p. 137-) Tlie quotients do 
T ^ 
^ A translation of thie valuable Memoir wHl be fouiid in this Journal, vol. HI, 
l>p. 1, 256.; IV. pp; 23, 262.; V.p, 28. ' ' 
