676 ZONES AND REGIONS [Pt. Ill, Sect. Ill 



length of one's finger. The comparison between individuals of the same 

 species in Scandinavia and in the arctic districts shows, as appears from the 

 following table, that this small size is not a specific peculiarity, but a reduc- 

 tion wrought by the environment. 



COMPARATIVE STATURE OF PLANTS IN SCANDINAVIA 

 AND IN THE POLAR DISTRICTS. 



The reduction extends to the growth in length and thickness of epigeous 

 axes as well as to the growth in surface of leaves. The roots, however, 

 like those of plants in dry stations, appear to attain relatively large 

 dimensions. 



A few measurements made by Kjellman show the diminutive size of 

 foliaged shoots in the tundras. In the beginning of August the year's 

 shoots of Salix polaris (Fig. 403), which had then reached their full 

 length, varied between 1 and 5 mm., and only in a few cases attained 

 9-1 1 mm. Each year's shoot possessed two or three leaves, the length 

 of which varied between 7 and 11 mm., and the breadth between 5 and 

 11 mm. The year's shoot of Ledum palustre, which even at Hapar- 

 anda, only a little more to the south, attained 130 mm., was 8 to 30 mm. at 

 Pittlekaj, averaging about 20 mm. ; its leaves were small and narrow. The 

 leaves of Vaccinium Vitis-Idaea (Fig. 402) were scarcely 4 mm. long and 

 3-5 mm. broad ; those of V. uliginosum (Fig. 402) seldom more than 5 mm. 

 long. Herbs appear, for the most part, to be much less reduced, and 

 some, like Sieversia glacialis, Nardosmia frigida, and Saxifraga punctata, 

 even attain somewhat large dimensions. 



The secondary growth in thickness of axes diminishes to the north still 

 more rapidly than does their growth in length, so that Middendorffat first 

 mistook the last of the upright trees for young trees on account of their 

 slender forms. At the extreme limit, however, the growth in length is 

 strongly affected. 



Measurements of the number and thickness of the annual rings near the 

 limit of trees have been made by Middendorff and Kihlman. The latter 

 observer, for instance, in the stem of a little juniper-tree 83 mm. thick at 



