548 FREEZING AND BUUXIXG. 



at an altitude of 2343 metres, and 40 cm. below the surface, —5-3°; on the north 

 side of the summit of the Blaser, at Trins, at an altitude of 2239 metres, 40 cm. 

 below the surface, —40°; on the northern slopes of the Patscherkofel, at Inn.sbruck, 

 1535 metres above the sea-level, 60 cm. below the surface, —2-9°. The layer of snow 

 lying on the ground at these three points was not a thick one, and varied from 30 

 to 60 cm. Where the snow-layer was at least three times as thick, the minimum 

 thermometer gave the following results: On the south side of the summit of the 

 Blaser, at Trins, at an altituile of 2239 metres, 40 cm. below the surface, +0-1°; 

 rather lower on the same mountain, viz. at an altitude of 2086 metres, near the 

 cottage of my experimental garden, under a snow-drift 3 metres thick, -f 0-2°; on 

 the Patscherkofel, at Innsbruck, 1921 metres in height, in the vicinity of Kreuz- 

 brunnen, 65 cm. below the surface of the ground, -j-01°; near the Heiligwasser, 

 at Innsbruck, at an altitude of 1261 metres, where the winter coat of snow had 

 attained a thickness of almost 2 metres, 75 cm. below the surface, -|-1'35°. These 

 statements sufficiently show what a great significance is to be assigned to snow as 

 a protective measure against cold in those regions which are not deprived of the 

 sun in winter-time. While the temperature of the soil penetrated by roots of plants 

 sank even under deep snow to — 20° on the winter station of the Vega in Siberia, 

 the soil occupied by the roots of plants on the Alpine heights of the Tyrol in places 

 covered with abundant snow, was never once frozen, and where the snow layer was 

 very thin, was cooled down only to — 5"3°. Accordingly in the Alps, and generally 

 in high mountains of the north temperate zone, a thick layer of snow plays the 

 part of an excellent protective measure to the soil, and consequently to the plants 

 rooted therein. 



There are also plants in Alpine regions which are apparently dependent upon 

 this protective measure, and whose structure makes it possible for them to survive 

 through the severe winter hidden under thick masses of snow. To these belong, 

 in the first place, numerous bush-like woody plants of which Piiius humilis 

 represented opposite may serve as an example. The stems of these pines ai'e 

 not erect like those of other species, but assume a horizontal position even when 

 they attain a considerable thicloiess. Stems of even 20 cm. diameter, which would 

 certainly be able to sustain the ample crown in an erect position, grow almost 

 parallel to the ground without, however, directly resting upon it. In this respect 

 it is very remarkable that on the slope of the mountain the growing end of the 

 stem is always directed towards the valley, and it is also noticeable that this 

 peculiar habit of growth occurs not only in the mountain pines growing wild in 

 the Alps, but also in those raised from seed in the botanic gardens of towns, and 

 must therefore be regarded as an inherent peculiarity. The boughs and twigs which 

 curve upwards from the main stems are exceedingly elastic, and when presseil 

 down stretch themselves out along the gi-ound. Since all the boughs of the crown 

 are turned upwards, we get here a considerable accumulation, so that in many old 

 clumps of mountain pines the numerous boughs are so thickly crowded and so closely 

 interwoven that progress through them is almost impossible. The extensive tracts 



