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Key to Boletus in North America (Page Seven)

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[Pore surface not red or orange; pore surface not bruising blue to greenish blue; cut flesh not staining blue to bluish on exposure.]

Note: This key is in bad need of revision. The non-dichotomous format is annoying and, with the hindsight of a few years, I see many areas that require different emphasis, fleshing out, paring down, and so on. Don't hold your breath waiting, but I will eventually revise the key completely.

  • Found west of the Rocky Mountains, excluding Texas. (1/2)

    Page Ten

  • Found east of the Rocky Mountains, or in Texas. (2/2)

      > Mature pore surface and/or spore print with olive shades. (1/2)

      > Mature pore surface creamy to yellowish or brownish, without olive shades; spore print yellowish or brownish, without olive shades (see also Gyroporus.) (2/2)

        ° Stem not reticulate, or merely finely so the the extreme apex. (1/2)

          ~ Cap whitish, maturing to dingy buff. (1/2)

          Xanthoconium stramineum

          ~ Cap more highly colored. (2/2)

            * Ammonia on cap surface producing a green to blue-green reaction. (1/2)

              * Cap 3-11.5 cm, reddish to purplish; pore surface bruising brownish; stem brownish; spores 8-14 x 3-4 µ. (1/2)

              Xanthoconium purpureum

              * Cap 6-20 cm, variable in color but with lilac brown shades when young; pore surface not bruising; stem whitish with areas flushed with the cap color; spores 12-16 x 3.5-5 µ. (2/2)

              Boletus separans

            * Cap surface reaction to ammonia not green or blue. (2/2)

              * Growing under hardwoods or conifers; young cap dark brown to yellow-brown; spores 12-16 x 3-4 µ; widely distributed east of the Great Plains. (1/3)

              Xanthoconium affine

              * Growing under hardwoods; young cap golden brown; spores 10-12 x 2.5-3.5 µ; known from North Carolina. (2/2)

              Xanthoconium chattoogaensis

              * Growing under birch and hemlock; young cap whitish; spores 10-13 x 3-4.5 µ; known from Pennsylvania. (3/3)

              Xanthoconium montaltoense

        ° Stem reticulate. (2/2)

          ~ Stem coarsely reticulate. (1/2)

          ~ Not as above; reticulation present but not coarse. (2/2)

            * Cap grayish brown to yellow brown; stem white with brownish reticulation; ammonia on cap surface purplish red, or with a very pale bluish flash; spores 10-13 x 4-5 µ. (1/4)

            Boletus atkinsonii

            * Cap brownish yellow to yellow; stem white, becoming bright yellow towards apex; ammonia on cap dark purplish red; spores 10-17 x 4-6 µ. (2/4)

            Boletus gertrudiae

            * Cap dark red to maroon; stem yellowish with reddish streaks and a white base; ammonia on cap greenish blue; spores 8-14 x 3-4µ. (3/4)

            Xanthoconium purpureum

            * Cap lilac brown; stem whitish or flushed with brownish lilac; ammonia on cap deep bluish green; spores 12-16 x 3.5-5 µ. (4/4)

            Boletus separans

    Cite this page as:

    Kuo, M. (2003, June). Key to Boletus in North America (page seven). Retrieved from the MushroomExpert.Com Web site:

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