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The Genus Boletus [ Basidiomycetes > Boletales > Boletaceae . . . ] by Michael Kuo The mushrooms in Boletus, as the genus is traditionally defined, are boletes that do not typically have scabers or glandular dots on their stems. Their spore prints are olive brown to brown (a few species with yellowish or rusty spore prints, often included in Boletus, are officially placed in Xanthoconium but are treated here with Boletus). They have solid stems, and their pores are not typically elongated and radial (as in some species of Suillus). Under the microscope, their spores are not ornamented. Boletus is currently the largest genus of boletes, containing over 150 species in North America--but the writing is on the wall and it is clear that big taxonomic changes are coming soon to a Boletus in your viewing area. Check out just about any recent DNA survey of the boletes (this one from Hibbett & Binder, 2004, is handily online), and you will soon discover that "Boletus" is an incoherent label, genetically. The trouble is, we are still at the broad survey stage, and the hard work of collecting and testing the many hundreds and thousands of specimens that will be required in order to assert species and genera with confidence hasn't even started. Identifying species of Boletus, therefore, should be placed in contemporary context: much of what we thought we knew is likely to be upturned in the near future. Identifying Boletus species has never been particularly easy, anyway; it has always been a frustrating endeavor (though not quite as frustrating as identification in Leccinum), and one is constantly finding mushrooms that do not quite fit any description. To have much success with identification, you will definitely need to have fresh specimens representing several stages of development; the mushrooms in Boletus often change their appearance rather drastically as they develop. Specific identification pitfalls include cap color and bruising or staining changes. In general, color is one of the most unreliable features for mushroom identification (which is why looking at photos in field guides is an unsuccessful way to identify mushrooms!) . . . but with mushrooms in Boletus, one is especially likely to encounter problems with cap color. A mushroom described as having a black cap is not likely to have a white one, of course, but the brownish- and reddish-capped mushrooms in Boletus (which is most of them) are frequently variable in color, and subject to color changes due to weather conditions. As far as bruising or staining goes, you will need to be sure to check such reactions with fresh mushrooms, preferably within an hour of picking them. Waiting too long may produce unreliable results. And do not be surprised if you encounter faint staining or bruising where it should not happen, according to many descriptions. |
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