Appearance
The spores are 9–12 × 5–6 µm, ellipsoid, and are not amyloid; their surface is smooth. They are yellow in Melzer's reagent. The basidia have dimension of 46–62 × 7–10 µm, and are tetrasporic with short, stubby sterigmata. They have neither pleurocystidia nor cheilocystidia.The cap cuticle has a width of 250 to 450 µm and consists of loopshaped, dark hyphae with a width from 2 to 3 µm, which form an ixocutis and possess clamp connections; the fungus has no hypocutis. The gill trama consists of hyphae about 3 to 8 µm thick; the cap tissue comprises radial hyphae.
The mycorrhiza, formed from ''H. olivaceoalbus'' as a fungal partner, such as the ''Piceirhiza gelatinosa'', is white and has a smooth, waxy surface, with several layers of hyphae layered around the tree's roots; sometimes this mycorrhiza shows hypertrophy. The hyphae are covered with a jellylike mass that is secreted from the outer walls of the hyphae. The ectomycorrhizae can reach lengths of up to 10 mm and have few side branches; many older ectomycorrhizae have a cavity at the tip that resembles a hole.
Naming
''H. olivaceoalbus'' shows similarities between other closely related fungi of the genus ''Hygrophorus'', some of which have only minor differences in physical features. Examples include ''H. pustulatus'', ''H. inocybiformis'', ''H. tephroleucus'' or ''H. morrisii''. In the field, ''H. olivaceoalbus'' is distinguished by a combination of features including the double velum, the dark streaks on the slimy cap, the nattering of the stem, and growth under pines, as well as by microscopic characteristics. There is no risk of confusing it with toxic fungi.''Hygrophorus persoonii'' and ''H. olivaceoalbus'' produce different mycosterine and their flesh react differently with the addition of NaOH . Furthermore, ''H. persoonii'' favours oaks as a mycorrhizal partner. The North American species ''H. inocybiformis'' produces a smaller fruit body with caps measuring 3–6 cm wide, and dry stems that measure 3–6 cm long by 0.5–1.2 cm thick.
Distribution
''Hygrophorus olivaceoalbus'' creates mycorrhizae with conifers. In the West Coast of the United States, associations are most common with Sitka spruces and giant redwoods. In the Rocky Mountains it associates with Engelmann spruce and blue spruce, and in northeast North America with hemlocks. It usually favours acidic and chalky ground with mosses in higher altitudes as well as conifer forests and occasionally mixed forests. The fruit bodies are often found singly, but may also grow in clusters.The range of ''H. olivaceoalbus'' stretches across the northern and western North America as well as across Europe and Russia. The fungus typically fruits between late summer and early winter, and occasionally as early as June or right through December. The population is currently not endangered, except in France, where it is almost extinct.
Habitat
''Hygrophorus olivaceoalbus'' creates mycorrhizae with conifers. In the West Coast of the United States, associations are most common with Sitka spruces and giant redwoods. In the Rocky Mountains it associates with Engelmann spruce and blue spruce, and in northeast North America with hemlocks. It usually favours acidic and chalky ground with mosses in higher altitudes as well as conifer forests and occasionally mixed forests. The fruit bodies are often found singly, but may also grow in clusters.The range of ''H. olivaceoalbus'' stretches across the northern and western North America as well as across Europe and Russia. The fungus typically fruits between late summer and early winter, and occasionally as early as June or right through December. The population is currently not endangered, except in France, where it is almost extinct.
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