The limber pine stands in the shadow of threatened extermination by blister rust. This fungus disease, which attacks, girdles, and destroys all species of 5-needled pines, has wrought havoc in many parts of the country. Like so many virulent forest diseases, it was introduced from abroad. Since no known natural checks on it exist in this country, it is almost impossible to eradicate. It spreads to pines only from its alternate hosts, wax currant and other species of _Ribes_; if these are eradicated from the vicinity, the pines can be preserved. Though such control measures are costly, without them the limber pine might be lost forever from the park. The Government has been doing this work in selected forests on the northeast slope of Longs Peak and near Estes Cone, where many splendid specimens of this tree occur. Above Treeline Above the Subalpine zone, whose upper limit is treeline, lies the Alpine, or Arctic-Alpine, zone. This is the distinctive “Land of Lilliput” of the plant kingdom, the alpine tundra, where nearly all existing plant species are in dwarf form. Some of the zone is barren rock, with only algae and lichen growth. Vast expanses of it, however, are covered with a cold, wet soil mantle which, during the brief summertime, presents a myriad of low, cushionlike flower clumps. Sometimes—usually through July—the effect is that of a vast carpet of flowers. The list of plant species is great. Showiest of the alpine flowers are ALPINE BUTTERCUP, with large, yellow, poppylike flowers, often blooming at the very edges of snowbanks; ALPINE FORGET-ME-NOT, which grows in dense, low clumps and presents thick patches of bright-blue flowers; MOSS SILENE (“moss campion”), a mosslike cushion plant with pink flowers (also found in Greenland and Alaska); GRAYLOCKS ACTINEA, sometimes called “Old Man of the Mountain,” with bright-yellow flower heads, usually wind-blown and ragged, almost as broad as the plant is tall; TUFTED PHLOX, better known here as “alpine phlox,” the cushion of which is sometimes entirely covered with pale-blue or white flowers; AMERICAN BISTORT, with dense spikes of tiny flowers standing like miniature bottle brushes above the tundra grasses; KINGS CROWN, a fleshy plant with dark-red blossoms, the whole plant often turning completely red in late summer; and MT. WASHINGTON DRYAD, with its curious 8-petaled, cream-colored flowers. [Illustration: Limber pine at treeline.]