Description: Like many other mushrooms, L. indigo develops from a nodule, or pinhead, that forms within the underground mycelium, a mass of threadlike fungal cells called hyphae that make up the bulk of the organism. Under appropriate environmental conditions of temperature, humidity, and nutrient availability, the visible reproductive structures (fruit bodies) are formed. The cap of the fruit body, measuring between 5 and 15 cm (2.0 and 5.9 in) in diameter, is initially convex and later develops a central depression; in age it becomes even more deeply depressed, becoming somewhat funnel-shaped as the edge of the cap lifts upward. The margin of the cap is rolled inwards when young, but unrolls and elevates as it matures. The cap surface is indigo blue when fresh, but fades to a paler grayish- or silvery-blue, sometimes with greenish splotches. It is often zonate: marked with concentric lines that form alternating pale and darker zones, and the cap may have dark blue spots, especially towards the edge. Young caps are sticky to the touch.