Multifurca also represents the likely sister group of Lactarius (see phylogeny, right). furcatus was moved to the new genus Multifurca, together with some former Russula species. Molecular phylogenetics uncovered that, while macromorphologically well-defined, milk-caps were in fact a paraphyletic genus as a consequence, the genera Lactifluus was split from Lactarius, and the species L. The name "Lactarius" is derived from the Latin lac, "milk". torminosus was accepted as the new type of the genus after the splitting-off of Lactifluus as separate genus. The genus Lactarius was described by Christian Hendrik Persoon in 1797 with L. Several species have preferences regarding soil pH and humidity, which will determine the habitats in which they occur. pubescens with birch, will rather occur in early stages. However, species symbiotic with early colonizing trees, such as L. Lactarius species are considered late-stage colonizers, that means, they are generally not present in early-colonizing vegetation, but establish in later phases of succession. For most tropical species, host plant range is poorly known, but species in tropical Africa seem to be rather generalist. Other examples of specialized associations of Lactarius are with Cistus shrubs (L. lilacinus), some of which even evolved specificity to one of the Alnus subgenera. A well-studied example is that of alders, which have several specialized Lactarius symbionts (e.g. While most species display a preference towards either broadleaf or coniferous hosts, some are more strictly associated with certain genera or species of plant hosts. Lactarius pyrogalus mainly associates with common hazel. Confirmed habitats apart from temperate forests include arctic tundra and boreal forest, mediterranean maquis, tropical African shrubland, tropical Asian rainforest, mesoamerican tropical oak forests, and Australian Eucalyptus forests. As such, they are dependent on the occurrence of possible host plants. Lactarius belongs to a lineage of ectomycorrhiza obligate symbionts. While there are some easily recognizable species, other species can be quite hard to determine without microscopical examination. The habitat and especially the type of host tree can also be critical. Characters important for identification of milk-caps (Lactarius and Lactifluus) are: initial colour of the latex and color change, texture of cap surface, taste (mild, peppery, or bitter) of latex and flesh, odor, and microscopical features of the spores and the cap cuticle (pileipellis). All known annulate and pleurotoid (i.e., laterally stiped) milk-caps, on the contrary, belong to Lactifluus. Species identification Distinguishing Lactarius from Lactifluus based on morphology alone is difficult there are no synapomorphic characters known so far that define both genera unequivocally but tendencies exist: zonate and viscose to glutinose caps are only found in Lactarius, as well as closed (angiocarpous) and sequestrate fruitbodies. Unlike Russula, Lactarius also have lactiferous, i.e. The trama (flesh) contains spherical cells that cause the brittle structure. Microscopically, Lactarius species have elliptical, rarely globoid spores with amyloid ornamentation in the form of more or less prominent warts or spines, connected by ridges, like other members of the family Russulaceae. Some species have angiocarpous, i.e., closed fruitbodies. Spore print color is white to ocher or, in some cases, pinkish. the blue Lactarius indigo or the orange species of section Deliciosi. Dull colors prevail, but some more colorful species exist, e.g. Several species have pits (scrobicules) on the cap or pileus surface. Cap surface can be glabrous, velvety or pilose, dry, sticky or viscose and is often zonate. Fruitbodies are small to very large, gilled, rather fleshy, without veil, often depressed or even funnel-shaped with decurrent gills. The milk or latex emerging from bruised flesh is often white or cream, but more vividly coloured in some species it can change upon exposition or remain unchanged. The eponymous "milk" and the brittle consistency of the flesh are the most prominent field characters of milk-cap fruitbodies. Lactarius indigo is one of the most strikingly colored Lactarius. Spores of Lactarius alnicola showing a reticulate (net-like) ornament with an amyloid stain reaction. Lactarius quietus exuding cream-colored latex from gills upon cut.
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