BOOK V. 
GEOGRAPHY. 
485 
From what has now been said, all that is apparent is, that, 
as we ascend in the atmosphere, temperature diminishes and 
light increases in a proportion corresponding, to a certain 
degree, with the climate of higher latitudes ; but even to this 
there are exceptions, depending upon particular circum- 
stances, and especially upon the amount of summer heat, of 
which more will be said presently. Thus, at Enontekissi, in 
Lapland, in 68° 30^ N. lat., at an elevation of 1356 feet above 
the sea, a climate which, from its situation, should be scarcely 
clothed with herbage. Von Buch found corn, orchards, and a 
rich vegetation. 
Having now seen what great differences are produced in 
the characters of vegetation by elevation above the sea, let us 
next take a view of the influence caused by latitude. In the 
countries lying near the equator, the vegetation consists of 
dense forests of leafy evergreen trees, palms, and arborescent 
ferns, among which are intermingled epiphytal herbs and 
rigid grasses : there are no rich verdant meadows, such as 
form the chief beauty of our northern climate ; and the lower 
orders of vegetation, such as mosses, fungi, and confervae, are 
very rare : Myrtaceae, Melastomaceae, Musaceae, Piperacese, 
Scitamineae, and frutescent Compositae abound. As we re- 
cede from the equator these gradually give way to trees with 
deciduous leaves, to Coniferae, Rosaceae, and Amentaceae ; 
rich meadows appear, abounding with tender herbs ; the 
epiphytal Orchideae disappear, and are replaced by terres- 
trial fleshy-rooted species ; mosses clothe the trunks of aged 
trees : decayed vegetables are covered with parasitical fungi ; 
and the waters abound with Confervas. Approaching the poles, 
trees wholly disappear; dicotyledonous plants of all kinds 
become comparatively rare ; and grasses and cryptogamic 
plants constitute the chief features of vegetation. To what 
cause, except that of temperature, and perhaps light, these 
effects are to be ascribed, is unknown. They are found to 
exist equally towards either pole ; and it is evident, from the 
uniform manner in which the influence of the controlling 
cause, whatever it may be, is exercised, that the laws under 
which the geographical distribution of plants is determined, 
I I 3 
