Distinguishing Characters: Boletoid stature; pileus yellowish, pallid yellowish brown to pallid pinkish brown, glabrous and lacking fibrils or fibrillose scales, subglutinous; pore surface yellowish, shallowly depressed to subdecurrent, not bruising or only slightly so; stipe not conspicuously glandulose, though obscure glandulae are present that become darker when handled, whitish to dull yellow, some vinaceous staining developing toward base; veil lacking; spores ellipsoid to subcylindric, smooth, 8.0-9.6 x 3.0-4.0 Âµm; growing in association with conifers, especially Ponderosa pine - Pinus ponderosa P. & C. Lawson.
Compare: Suillus brevipes - pileus dull reddish or orangish brown to dark reddish brown; stipe not glandulose or only weakly so; veil lacking; spores 7.0-9.0 (10) x 3.5-4.0 Âµm. Suillus kaibabensis - pileus yellowish, pallid yellowish brown to pallid brown, pore surface lacking reddish glandulae, stipe glandulose, vinaceous stains developing toward base; spores 7.6-9.5 x 3.2-4.5 Âµm. Suillus subaureus - pileus pallid yellowish background covered with appressed reddish brown tomentum or fibrilose scales; pore surface typically not staining or staining slowly; stipe lacking glandulae at first, becoming noticeably glandulose with age; spores 7.0-10.0 x 2.7-3.5 Âµm. Suillus wasatchicus - pore surface covered in conspicuous reddish glandulae, particularly noticeable when immature; stipe conspicuously glandulose, lacking vinaceous stains toward base; spores 8.0-10.4 x 1.5-2.0 Âµm.
Bassette, A.E., W.C. Roody and A.R. Bessette. 2000. North American Boletes: A Color Guide to the Fleshy Pored Mushrooms. Syracuse University Press, Syracuse.
Thiers, H.D. 1975. California Mushrooms: A Field Guide to the Boletes. Hafner Press, New York.
Thiers, H.D. 1976. Boletes of the Southwestern United States. Mycotaxon 3: 261-273.
Smith, A.H. and H.D. Thiers. 1964. A Contribution Toward a Monograph of North American Species of Suillus. Privately publish