[Illustration: Indian paintbrush is common at all elevations below tundra. It may be white, yellow, orange, pink or red. The actual flowers, inconspicuous and green, are surrounded by brilliantly colored bracts. Semi-parasitic on other plants, paintbrush is normally found growing in conjunction with other wildflowers; its roots steal sustenance from neighboring plants.] [Illustration: Yellow stonecrop, widely distributed in forest and scrub-forest zones, is one of the park’s few plants having succulent leaves, an adaptation that helps it survive in such situations as dry, rocky outcrops.] [Illustration: The Calypso orchid grows in the cool, shadowed forest where light is dim. It lives in partnership with certain fungi that exist about the orchid’s roots and seem to help nourish it.] [Illustration: Silky lupine, a legume, has nitrogen-fixing nodules on its roots, thus allowing it to grow in nitrogen-poor soil. It is widely distributed in grassland and forest communities.] Fire Succession: Key to Continuity Most of Glacier’s fires are lightning-caused. Strikes may flare up immediately; or fires may smolder in the forest duff for days until fanned into flame by wind. _Ground fires_ may race through the forest understory, causing minor damage; or they may bridge the understory and reach the canopy, thus becoming rapidly spreading _crown fires_. Under certain conditions, uncontrollable infernos may develop, generating terrific winds and heat. These rare conflagrations are called _fire storms_. Every type of forest habitat has _climax vegetation_—trees and shrubs that are best suited to the site and thus maintain themselves indefinitely if not disrupted. After a major fire, habitat conditions are usually so altered that the site must pass through several _seral stages_ before conditions are such that climax vegetation can return. A _sere_ is a series of plant communities that follow one another in orderly fashion until climax conditions are again reached. [Illustration: Lightning fires occur most often during the hot, dry weeks of late summer.] [Illustration: When the forest is dry, lightning often causes quick flare-ups.] [Illustration: The forest may continue to burn for days after the main conflagration has passed.] [Illustration: After a major fire, sun-loving grasses, shrubs, and wildflowers quickly invade the former forest. Deer and wapiti benefit from these new food sources.] [Illustration: Lodgepole pine, a pioneer species quick to take over burned areas at lower elevations, grows rapidly. These trees are five years old.] [Illustration: This is a Glacier National Park forest 80 years after a major fire.]