ALPINE PLANT. A plant whose natural habitat is in high altitudes. These plants form one of the three great climatic groups of xerophytes (q.v.), and have in general the ordinary xerophy tic• adaptatious. Among the leading peculiarities of Alpine vegetation there may he noted (1) The gnarled and twisted aspect of the shrubs and trees; so characteristic is this habit in the mountain pine of Europe that the tree has been called by the Germans Krumntho/z, i.e., "crooked wood." (2) The vegetation is notably dwarfed. (3) The plant axes are commonly horizontal rather than vertical, and as a result there is a great number of creeping plants. ( 4 ) The "cushion (Ger. Polstcr) habit," so common else where in mosses, is found in many seed plants, which sometimes resemble brain coral in gen eral effect. (5) The rosette habit is frequent. (6) The flowers and roots of Alpine plants, in striking contrast to the stems and leaves, are not reduced; they may even be increased. This com bination makes the roots and flowers appear gigantic, and travelers, as a consequence. are always struck with the relatively large floral development. (7) Alpine leaves show decidedly xerophytic structures, many plants having thick skinned, leathery evergreen leaves, as the pines and rhododendrons, while others have hairy leaves, as the edelweiss. Kerner, Die Abban gig•eit der Plian,:engestalt ton Klima and Boden (18(19), and Bonnier, Cultures experimentales dens lcs hautes altitudes 1888 to date) ,have car ried on some remarkably interesting experiments to determine the influence that Alpine climates exert upon plants. Lowland plants were taken into Alpine regions and were found to assume structural adaptations similar to those normally found in Alpine plants but not normally found under lowland conditions. In particular, sub terranean organs were found to increase in size, while aerial stems became reduced and tended toward horizontality. The leaves became small er and thicker and often inure hairy; sometimes the leaves showed more red coloration. The flowers became relatively, and in some eases absolutely, larger and more highly colored, and blossoming often took place earlier than in the lowlands. Structurally the leaves showed a
thicker cuticle and increased development of palisade cells. Bonnier found that these plants increased in Alpine characters year by year, and that. when taken again to the lowlands, the Al pine features were not lost for a long time. In general, the adaptations of Alpine plants are sim ilar to those of Arctic plants, but it has been noticed that the leaves are thinner and show inure differentiation, intercellular spaces are fewer, and palisade cells better developed. Hairy plants are perhaps more characteristic of Alpine than of Arctic regions. The Alpine conditions are peculiar and are chiefly due in the last analysis to the rarefied air. The consequent decrease in pressure has probably a direct. effect on vegetation, but experiments have not yet made this clear. In any event, the thin air causes a greatly increased in tensity of heat and light by day, and a great ly increased radiation of heat by night. Thus great extremes of temperature are the rule. The rarity of the air also prevents great rain fall. These conditions, together with exposure to wind, work in harmony toward the develop ment of a highly xerophytic flora, as has been previously mentioned, and it is easy to see how none but xerophytes can survite in such a loca tion. The differences between Arctic and Alpine conditions may be summed up thus: Arctic light is more constant, but less intense, and this perhaps accounts for the differences in leaf structure and color intensity in Arctic and Alpine regions, as stated above. The changes of temper ature are more rapid in Alpine districts. The xerophytic structures of Alpine plants are per haps due to causes set in operation by thin air, while in Arctic plants the causes may lie set in operation rather by the cold or even frozen soil. See also MOUNTAIN PLANT, and the plate showing ALPINE VEGETATION, accompanying this article.