552 ' THE VEGETABLE WORLD. 
table organisation is subject to the same laws, and experiences 
loss of power and vigour proportioned to the decrease of heat. 
But a natural reflection presents itself immediately, as a corollary 
upon these remarks. 
When we ascend a mountain, or, in fact, when we ascend by 
any means whatever,—in a balloon, for instance, as Mr. Glaisher’s 
experiments seem to show,—the temperature decreases by something 
like one degree for every hundred yards above the surface. It 
follows from these premises that every stage in the ascent of a 
mountain should exhibit different forms of vegetation, each form- 
ing a zone or botanic region, similar to those we have passed in 
tracing their geographical latitudes. And this is so in fact, as we 
shall find in the following remarks, which we borrow from the 
writings of Adrien de Jussieu on the vegetation of the Alps, 
Professor Ch. Martin, on Mount Ventoux in Provence, and Dr. 
Hooker, on the Himalayas :— 
“ Let us imagine a spectator at the foot of the Alps,” says M. 
de Jussieu, “ opposite to one of those grand rocky masses crowned 
with eternal snow. As his eye ranges along the sides of the 
mountain, he observes that the vegetation which immediately sur- 
rounds him, and which is that which characterises central and 
northern France, disappears at a certain height, giving place to 
another, which in turn disappears at a higher range. Beyond a 
certain distance the eye can only seize the masses indicated by 
large trees, the humbler plants being concealed behind them, 80 
that they look like a series of bands superposed one over the 
other on the slopes of the mountain. At first these belts are 
composed of deciduous-leaved plants, which drop early, and are 
readily distinguishable by their more tender verdure, than 
conifers of deeper green, which in the mass appear nearly black. 
Another belt succeeds of an undecided green, interrupted here and 
there by clumps of another colour, which goes straggling up to 
the sinuous line where the snow commences. This is owing to the 
circumstance that the trees whose branches are too closely inter- 
mingled have died out, making room for shrubs or herbaceous 
plants, more dwarfed in their growth, and more on a level with 
the soil. . ae 
“Tf the spectator approaches the mountain and scales it, he will ae: 
