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 

 conclusion 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 



