II. ASCENDING ZONES. 11 
2. AscENDING oR CLIMatTic Zonns. 
If a Botanist, while standing on the summit of one of our 
loftiest hills, will make out a list of all the plants he can see close 
around him, he will find that his list includes very few flowering 
plants. Suppose that, while slowly descending from summit to 
base, he carefully sets down the names of all the other phanero- 
gamous plants successively as they may come under his notice. 
His list will thus shew the highest point, or upper limit, attained 
by each species on that particular hill, and in that particular line 
of descent from its summit; of course, not the absolute heights, 
but the upper limits of the species relatively to each other, or one 
above another. 
If the Botanist should now reverse his course of observation, in 
ascending from base to summit, he will first make a much more 
numerous list of species at-and about his starting point at the foot 
of the hill. The species quite on the summit being very few, those 
of the base will be found gradually disappearing from his view as 
he ascends higher and higher towards that summit. At the same 
time, a smaller number of other species, not descending so low as 
the base of the hill, will gradually come under his notice ; some of 
which will again disappear from view, while probably some others 
will continue to be found at intervals nearly or quite up to the 
actual summit. All the species which were not seen at the base 
of the hill, and which first became obvious in succession during 
the ascent, may be said to have a lowest point, or lower limit on 
the hill supposed to be under examination. 
. By a further supposition, our Botanist shall make like observa- 
tions on some other adjacent hill, one of nearly equal elevation, 
and in the character of its surface also resembling the hill before 
ascended and descended. Often repeated experience warrants an 
expectation that the Botanist will find a nearly similar series or 
succession of species on this second hill, if comparing its plants 
with those on the former hill. He would never find two lists 
corresponding precisely, if so made on different hills. Some of 
the species seen on the one hill, might likely not be observed at all 
