66 FORESTRY OF NORWAY. 
spurges, distinguished by their poisonous or pleasant- 
flavoured sweet milk, as the case may be, manifest a 
peculiar formative power in nature; and the dragon-tree, 
in the garden of Crotava, in Teneriffe, a gigantic arbores- 
cent lily plant, shows itself the growth of thousands of 
years. 
‘We have thus passed through six different zones of 
vegetation, in which we have found the continually 
increasing temperature calling forth ever a different, and 
ever a more luxuriant vegetation. 
‘If, in the warm region we have reached, we ascend 
one of the mountains found there—say the Pic of Teyde— 
we shall find that we pass through similar zones, but in 
order they are reversed. 
‘Man has taken possession of the soil of the plain at the 
base of the mountain, and dislodged the original vegeta- 
tion. Through vineyards and maize-fields we ascend, till 
the shades of the evergreen bay-laurel surround us. Trees 
of the lace-bark tribe and similar plants succeed; we 
wander for a time through a zone of evergreen forest trees. 
At a height of 4000 feet we lose the plants which had so 
far accompanied us. 
‘A very small number of peculiar plants mark a quickly 
traversed zone of deciduous trees, and we come among the 
resinous trunks of the Canary pine. 
‘A zone of conifers shields us from the sun’s rays up to 
a height of 6000 feet; then the vegetation suddenly 
becomes low ; from humble bushes it passes into a flora 
which has all the characteristics of the Alpine plants, till 
finally the naked rock sets a limit to all organic life, and 
no snow and ice bedeck the summit of the mountain, only 
because its height of 12,236 feet does not, in a position so 
near the tropics, extend up to the region of eternal snow. 
‘Counting by the limits of vegetation, we have resur- 
veyed, in a few hours’ climb, the wide way from Spitzber- 
gen to the Canaries—an extent of more than fifty degrees 
of latitude. 
‘In the whole way, downwards towards the south, and 
