ARCTIC PLANTS. In many respects these plants, whose natural habitats are in high lati tudes, resemble alpine plants (q.v.), and, like them, form one of the three climatic groups of xerophytes (q.v.). Dwarf growth is one of the chief characteristics of Arctic vegetation, and is remarkably well illustrated in a juniper stern reported by Kihlman: The stem was but 3311 incites thick, and yet showed 544 growth rings. Plants that grow to a height of one or two feet in Sweden are but one or two inches high in the far North. As in the ease of alpine plants, re duction is confined to the stems and leaves, the roots^. and flowers being as large as in warmer climates. Cushion and rosette plants are well developed. The leaf structure is highly xero phytic, leathery and thick-skinned evergreen leaves being particularly abundant.
The Arctic life conditions have been especially well described by Kihiman (Pflunzenbiologisehe Studien ails llussisrh-Implund, I890. etc.). The cold and darkness of the long winter nights have but little influence on the vegetation. Of greater importance are the short vegetative period, which excludes many plant species from life in Arctic regions, and the prevalence of dry winds at times when transpiration losses cannot be made good. Kililman thinks that this latter factor is the chief cause of Arctic phenomena. The absence of trees, then, is due not to the shortness of the period of vegetation, nor to the cold, but to dry winds; this is shown by the fact that trees thrive in the coldest known place in the world (Verkhoyansk, Siberia). and also by the fact that the height of shrubs is determined by the level of the snow in winter. The continuous though not intense light of Arctic regions checks growth, but favors photosynthesis. One of the peculiarities of Arctic plant life is that there are no gradual seasonal transitions. The buds are largely laid down in the preceding season, and spring into active life at once; growth is checked with equal suddenness in the fall.
The Arctic differs radically from the temperate zone in that plant structures are xerophytic, re gardless of water and soil conditions. In fact, one may refer all of the Arctic vegetation t.0 one great plant formation, the tundra (q.v.). While Arctic plants closely resemble alpine plants eco logically, there are interesting floristic differ ences. Alpine plants (q.v.) are noted for their endemism (q.v.), while Arctic plants are similar ever wide areas. Indeed, the Arctic floras of Europe and America are almost identical.
About seventeen hundred species of plants have been found in the Arctic region. In the zone nearest the circle grow a few trees, mainly junipers, dwarf willows, and birches. The tree line in the Samoyed region ends near the 67th parallel of latitude; at the Yenisei River, near the 65t11 parallel; at the Lena, near the 71st parallel; at. the Mackenzie, near the 68th par allel; at Hudson Bay, it runs down to the 60th parallel; in Labrador, to the 52d parallel. fn Greenland it lies near the 62d parallel. Flower ing plants, grasses, mosses, and lichens extend to the most northern land seen by man. Examples of those found in all sections of the Arctic world are saxifrages (Saxifraga oppositifolia is ubiqui tous), several varieties of ranunculus, potentil las, poppies (the Arctic poppy, Papurer nudi caulP, is found even upon the crests of the cliffs in northern Greenland. where it thrusts its head through the edge of the ice-cap to reach the sun light), drabas, cochlearia, etc. The country richest in variety is Lapland, where are found three fourths of the species known in the Arctic regions. For the varieties characteristic of each country, see LAPLAND; GREENLAND; SIBERIA; ALASKA; SPITZBERGEN ; FRANZ-JOSEF LAND; ELLESMERE LAND; GRINNELL LAND, etc. See also Musci; LICIIEN ; GRASSES; DISTRIBUTION OF PLANTS, etc.