TEMPERATURE. 67 
upwards towards the summit of Teyde, vegetation varies 
conformably with the climatal conditions; and we can 
almost account for the observed distribution of plants by 
the mere increase and diminution of heat. If we extend 
our research further, we can even name particular plants 
which are found in particular northern latitudes, and in 
lower latitudes again regularly occur at particular heights 
on the mountains’ 
The geographical distribution of trees in Norway, which 
has been detailed, is to a very great extent the result of 
difference of temperature; and that this is the case will 
probably be admitted by all. But under this general 
zonclusion there are numerous phenomena, causes, effects, 
conditions, and results included. The results are the 
results of temperature under varied conditions, including 
amongst others, distribution in time, atmospheric pressure, 
and cloudy and cloudless skies. I have no intention to 
discuss here phenomena of meteorology and their effects 
on vegetation, and the effects of vegetation upon these. 
My present purpose extends only to the repeating of infor- 
mation collected in regard to facts and phenomena, and 
like the bricklayer’s labourer, handing these over to others 
to make of them what use they may. But for the 
further information of the general reader, I may cite some 
views in regard to the process of vegetation which I think 
may be interesting, and which I consider substantially 
sound. 
It is a generally recognised fact that heat is necessary 
to vegetation, and that without this, differing in the case 
of different plants, they will not grow, or if they grow 
they do not flower, or if they flower they do not fruit, 
or if they fruit they do not mature their seed, or if they 
mature their seed, the seed does not germinate and repro- 
duce the plant. But to give explicitness to such state- 
ments it is necessary to distinguish things which differ. 
The average heat of the summer is something different 
from the average heat of the year; the average heat of 
