All known annulate and pleurotoid (i.e., laterally stiped) milk-caps, on the contrary, belong to "Lactifluus". 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 curticle (pileipellis). The habitat and especially the type of host tree can also be critical. While there are some easily recognizable species, other species can be quite hard to determine without microscopical examination. "Lactarius" is one of the most prominent genera of mushroom-forming fungi in the Northern hemisphere. It also occurs natively in Northern Africa, tropical Africa, tropical Asia, Central America, and Australia. Its possible native distribution in South America and different parts of Australasia is unclear, as many species in those regions, poorly known, might in fact belong to "Lactifluus", which has a more tropical distribution than "Lactarius". Several species have also been introduced with their host trees outside their native range, e.g. in South America, Southern Africa, Australia, and New Zealand. "Lactarius" belongs to a lineage of ectomycorrhiza obligate symbionts. As such, they are dependent on the occurrence of possible host plants. 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. 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. A well-studied example is that of alders, which have several specialized "Lactarius" symbionts (e.g. "L. alpinus", "L. brunneohepaticus", "L. lilacinus"), some of which even evolved specificity to one of the "Alnus" subgenera. Other examples of specialized associations of "Lactarius" are with "Cistus" shrubs ("L. cistophilus" and "L. tesquorum"), beech (e.g. "L. blennius"), birches (e.g. "L. pubescens"), hazel (e.g. "L. pyrogalus"), oak (e.g. "L. quietus"), pines (e.g. "L. deliciosus"), or fir (e.g. "L. deterrimus").