BOTANICAL INFORMATION. 201 
comprehensive than the design, may be held something better 
than a mere fragment of a large work. 
[The following fragments are given by Mr. Watson, as 
examples of the proposed volumes.—Ep ] 
Botanical Geography of Britain.—* Climatic or Ascending 
| Zones of plants are designed to indicate their relative distri- 
bution under the joint influence ofaltitude and latitude, with 
other conditions of a more local character, such as proximity to 
Seas or mountains, the state of exposure or shelter, &c. It 
has been explained, that connexions may be traced between 
each of these conditions singly; but that everywhere the in- 
fluence of any one is more or less disturbed and modified by 
that of others. Their effect upon the flora or general vegeta- 
tion is mostly indirect or remote; that is, the flora varies 
with the climate, and the climate varies with altitude, lati- 
tude, and other conditions of place and surface. On a single 
isolated mountain the ascending zones of vegetation are very 
strongly marked, in accordance with altitude; some species 
disappearing, other species appearing, one above another, as 
We gradually ascend from base to summit. Yet on a single 
mountain we may see that local changes in the character of 
its surface, and the differences of aspect on its declivities, whe- 
ther facing to or from the sun, will disturb the regularity of its 
ascending zones. On an extended range of mountains the — 
disturbing effect of local peculiarities will become much more — 
Obvious, And when we have fo adapt our zones to several 
groups of mountains, dissimilar in extent, elevation, lai atud Bs 
maritime proximity, and other circumstances, it then becomes 
difficult to define them with any exactness. We experience this 
difficulty in tracing the ascending zones of plants in Britain. 
The absolute elevation at which the same species will grow, 
varies by many hundred feet on different mountains. And as 
this variation is by no means uniform with different species, 
we find local changes in their relative elevation also, the limit | 
E of one being compared with thelimitofanother.Notwithstand- ——— 
Mg Such local exceptions, however, the general rule will be a 
