Lactarius indigo

''Lactarius indigo'', commonly known as the indigo milk cap, indigo milky, the indigo (or blue) lactarius, or the blue milk mushroom, is a species of agaric fungus in the family Russulaceae. A widely distributed species, it grows naturally in eastern North America, East Asia, and Central America; it has also been reported in southern France. ''L. indigo'' grows on the ground in both deciduous and coniferous forests, where it forms mycorrhizal associations with a broad range of trees. The fruit body color ranges from dark blue in fresh specimens to pale blue-gray in older ones. The milk, or latex, that oozes when the mushroom tissue is cut or broken — a feature common to all members of the genus ''Lactarius'' — is also indigo blue, but slowly turns green upon exposure to air. The cap has a diameter of , and the stem is tall and thick. It is an edible mushroom, and is sold in rural markets in China, Guatemala, and Mexico. In Honduras the mushroom is called a chora, and it's generally eaten with egg; generally as a side dish for a bigger meal.

Taxonomy and nomenclature

Originally described in 1822 as ''Agaricus indigo'' by American mycologist Lewis David de Schweinitz, the species was later transferred to the genus ''Lactarius'' in 1838 by the Swede Elias Magnus Fries. German botanist Otto Kuntze called it ''Lactifluus indigo'' in his 1891 treatise '' Revisio Generum Plantarum'', but the suggested name change was not adopted by others. Hesler and Smith in their 1960 study of North American species of ''Lactarius'' defined ''L. indigo'' as the type species of subsection ''Caerulei'', a group characterized by blue latex and a sticky, blue cap. In 1979, they revised their opinions on the organization of subdivisions in the genus ''Lactarius'', and instead placed ''L. indigo'' in subgenus ''Lactarius'' based on the color of latex, and the subsequent color changes observed after exposure to air. As they explained:

The gradual development of blue to violet pigmentation as one progresses from species to species is an interesting phenomenon deserving further study. The climax is reached in ''L. indigo'' which is blue throughout. ''L. chelidonium'' and its variety ''chelidonioides'', ''L. paradoxus'', and ''L. hemicyaneus'' may be considered as mileposts along the road to ''L. indigo''.

The specific epithet ''indigo'' is derived from the Latin word meaning "indigo blue". Its names in the English vernacular include the "indigo milk cap", the "indigo Lactarius", the "blue milk mushroom", and the "blue Lactarius". In central Mexico, it is known as ''añil'', ''azul'', ''hongo azul'', ''zuin'', and ''zuine''; it is also called ''quexque'' (meaning "blue") in Veracruz and Puebla.

Description

Like many other mushrooms, ''L. indigo'' develops from a nodule, 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 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