in the Distribution of Vegetable Forms. 5 S 
(in the whole of France in the whole of Germany ; the 
Glumaceae (in France ,^^5, in Germany 4,) of the whole mass 
of phaenogamous plants. 
In the same way that the system of climates of the New Con- 
tinent differs essentially from that of the Old, on account of the 
unequal distribution of the heat among the different parts of the 
year, so also the system of agroupment of American plants has 
its peculiar features. It is to the new researches of botanical 
arithmetic that we owe the knowledge of these contrasts between 
the temperate zones of the two worlds. I have thrown together 
in the following Table, the results of the American Flora of 
Pursh and of the French Flora of M. Decatidolle. I have 
added certain coefficients of the' European frigid region, in or- 
der to show how much of a boreal character the American tem- 
perate region presents in the live families of Ericese (and Rho- 
dodendra), Coniferse, Amentaceae, Umbelliferse, and Labiatae. 
Temp. Temp. 
America. 1? ranee. Lapland. America. France, Lapland. 
Compositae, 
1 
F 
1 
• T 
0 
Malvaceae, x i ¥ 
1 
TTF 
0 
Glumaceae, 
1 
¥ 
1 
0 
Labiatae, 
5 0 
1 
2 4 
1 
70 
Gramineae alone, 
1 
To 
1 
1 0 
0 
Ericfeae and ^ 
Rhododendra, j ¥ F 
j 
1 
¥¥ 
Junceae alone. 
1 
1 
¥ J 
0 
T¥¥ 
Cyperaceae alone. 
1 
¥¥ 
1 
0 
Umbelliferae, 
1 
¥0 
1 
¥¥ 
Gruciferae, 
1 
T¥ 
0 
Amentaceae, 
1 
¥0 
1 
¥T 
Leguminosae, 
1 
1 
T¥ 
0 
Coniferae, 
¥0U 
TFO 
The differences which are manifested in this table between 
the two continents, bear, not merely upon the five last families, 
which might be called boreal forms^ but also upon the Gruciferae, 
the Junceae, and the Cyperaceae, which are equally rare in the 
torrid zone and in the temperate zone of the New Continent. 
It is conceived that the inquiries regarding the numerical 
proportions of vegetable families, will present results much more 
interesting when the Floras of different countries shall be cir- 
cumscribed within more precise geographical limits, and when 
botanists shall attend more particularly to the principles accord- 
ing to which varieties and species ought to be distinguished. 
The catalogues which we see under the vague name of Flora of 
the United States of America^ comprehend countries placed 
in very different climates, from 18 ° to 9° of mean temperature. 
Here we have a difference of climate as great as in Europe be-. 
